sparc64 is unique among architectures in taking the page_table_lock in
its context switch (well, cris does too, but erroneously, and it's not
yet SMP anyway).
This seems to be a private affair between switch_mm and activate_mm,
using page_table_lock as a per-mm lock, without any relation to its uses
elsewhere. That's fine, but comment it as such; and unlock sooner in
switch_mm, more like in activate_mm (preemption is disabled here).
There is a block of "if (0)"ed code in smp_flush_tlb_pending which would
have liked to rely on the page_table_lock, in switch_mm and elsewhere;
but its comment explains how dup_mmap's flush_tlb_mm defeated it. And
though that could have been changed at any time over the past few years,
now the chance vanishes as we push the page_table_lock downwards, and
perhaps split it per page table page. Just delete that block of code.
Which leaves the mysterious spin_unlock_wait(&oldmm->page_table_lock)
in kernel/fork.c copy_mm. Textual analysis (supported by Nick Piggin)
suggests that the comment was written by DaveM, and that it relates to
the defeated approach in the sparc64 smp_flush_tlb_pending. Just delete
this block too.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
I didn't find any possible modular usage in the kernel.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I didn't find any possible modular usage in the kernel.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I didn't find any possible modular usage of console_unblank in the
kernel.
This patch was already ACK'ed by Alan Cox.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Convert to proper kernel-doc format.
Some have extra blank lines (not allowed immed. after the function name)
or need blank lines (after all parameters). Function summary must be only
one line.
Colon (":") in a function description does weird things (causes kernel-doc
to think that it's a new section head sadly).
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Various core kernel-doc cleanups:
- add missing function parameters in ipc, irq/manage, kernel/sys,
kernel/sysctl, and mm/slab;
- move description to just above function for kernel_restart()
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Reorganize the preempt_disable/enable calls to eliminate the extra preempt
depth. Changes based on Paul McKenney's review suggestions for the kprobes
RCU changeset.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Changes to the base kprobes infrastructure to use RCU for synchronization
during kprobe registration and unregistration. These changes coupled with the
arch kprobe changes (next in series):
a. serialize registration and unregistration of kprobes.
b. enable lockless execution of handlers. Handlers can now run in parallel.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Changes to the base kprobe infrastructure to track kprobe execution on a
per-cpu basis.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The sys_ptrace boilerplate code (everything outside the big switch
statement for the arch-specific requests) is shared by most architectures.
This patch moves it to kernel/ptrace.c and leaves the arch-specific code as
arch_ptrace.
Some architectures have a too different ptrace so we have to exclude them.
They continue to keep their implementations. For sh64 I had to add a
sh64_ptrace wrapper because it does some initialization on the first call.
For um I removed an ifdefed SUBARCH_PTRACE_SPECIAL block, but
SUBARCH_PTRACE_SPECIAL isn't defined anywhere in the tree.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paul Mackerras <paulus@samba.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-By: David Howells <dhowells@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix more include file problems that surfaced since I submitted the previous
fix-missing-includes.patch. This should now allow not to include sched.h
from module.h, which is done by a followup patch.
Signed-off-by: Tim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The code for FUTEX_WAKE_OP calls an arch callback,
futex_atomic_op_inuser(). That callback can return an error code, but
currently the caller assumes any error is EFAULT, and will try various
things to resolve the fault before eventually giving up with EFAULT
(regardless of the original error code). This is not a theoretical case -
arch callbacks currently return -ENOSYS if the opcode they are given is
bogus.
This patch alters the code to detect non-EFAULT errors and return them
directly to the user.
Of course, whether -ENOSYS is the correct return value for the bogus opcode
case, or whether EINVAL would be more appropriate is another question.
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jamie Lokier <jamie@shareable.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
AIO was adding a new context's max requests to the global total before
testing if that resulting total was over the global limit. This let
innocent tasks get their new limit tested along with a racing guilty task
that was crossing the limit. This serializes the _nr accounting with a
spinlock It also switches to using unsigned long for the global totals.
Individual contexts are still limited to an unsigned int's worth of
requests by the syscall interface.
The problem and fix were verified with a simple program that spun creating
and destroying a context while holding on to another long lived context.
Before the patch a task creating a tiny context could get a spurious EAGAIN
if it raced with a task creating a very large context that overran the
limit.
Signed-off-by: Zach Brown <zach.brown@oracle.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds a connector that reports fork, exec, id change, and exit
events for all processes to userspace. It replaces the fork_advisor patch
that ELSA is currently using. Applications that may find these events
useful include accounting/auditing (e.g. ELSA), system activity monitoring
(e.g. top), security, and resource management (e.g. CKRM).
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove unused variable, and make code less evil that way. Fix whitespace
around for-loop-like macro.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This cleans spaces between * and pointer up, and adds "int" in "unsigned
int".
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Replace smp_processor_id() with any_online_cpu(cpu_online_map) in order to
avoid lots of "BUG: using smp_processor_id() in preemptible [00000001]
code:..." messages in case taking a cpu online fails.
All the traces start at the last notifier_call_chain(...) in kernel/cpu.c.
Since we hold the cpu_control semaphore it shouldn't be any problem to access
cpu_online_map.
The reason why cpu_up failed is simply that the cpu that was supposed to be
taken online wasn't even there. That is because on s390 we never know when a
new cpu comes and therefore cpu_possible_map consists of only ones and doesn't
reflect reality.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
!unlikely(expr) hurts my brain. likely(!expr) is more straightforward.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Do not transfer remaining time slice to another cpu on process exit.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I recently picked up my older work to remove unnecessary #includes of
sched.h, starting from a patch by Dave Jones to not include sched.h
from module.h. This reduces the number of indirect includes of sched.h
by ~300. Another ~400 pointless direct includes can be removed after
this disentangling (patch to follow later).
However, quite a few indirect includes need to be fixed up for this.
In order to feed the patches through -mm with as little disturbance as
possible, I've split out the fixes I accumulated up to now (complete for
i386 and x86_64, more archs to follow later) and post them before the real
patch. This way this large part of the patch is kept simple with only
adding #includes, and all hunks are independent of each other. So if any
hunk rejects or gets in the way of other patches, just drop it. My scripts
will pick it up again in the next round.
Signed-off-by: Tim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Combine a bit of redundant code between force_sig_info() and
force_sig_specific().
Signed-off-by: paulmck@us.ibm.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch removes checks for ->si_code == SI_TIMER from send_signal,
specific_send_sig_info, __group_send_sig_info.
I think posix-timers.c used these functions some time ago, now it sends
signals via send_{,group_}sigqueue, so these hooks are unneeded.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch simplifies some checks for magic siginfo values. It should not
change the behaviour in any way.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch replaces hardcoded SEND_SIG_xxx constants with
their symbolic names.
No changes in affected .o files.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Simplify the UP (1 CPU) implementatin of set_cpus_allowed.
The one CPU is hardcoded to be cpu 0 - so just test for that bit, and avoid
having to pick up the cpu_online_map.
Also, unexport cpu_online_map: it was only needed for set_cpus_allowed().
Signed-off-by: Paul Jackson <pj@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This change corrects an omission in posix_cpu_timer_schedule, so that it
correctly propagates the overrun calculation to where it will get reported
to the user.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch is a rewrite of the one submitted on October 1st, using modules
(http://marc.theaimsgroup.com/?l=linux-kernel&m=112819093522998&w=2).
This rewrite adds a tristate CONFIG_RCU_TORTURE_TEST, which enables an
intense torture test of the RCU infratructure. This is needed due to the
continued changes to the RCU infrastructure to accommodate dynamic ticks,
CPU hotplug, realtime, and so on. Most of the code is in a separate file
that is compiled only if the CONFIG variable is set. Documentation on how
to run the test and interpret the output is also included.
This code has been tested on i386 and ppc64, and an earlier version of the
code has received extensive testing on a number of architectures as part of
the PREEMPT_RT patchset.
Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Define jiffies_64 in kernel/timer.c rather than having 24 duplicated
defines in each architecture.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Back about a year ago when I last fiddled heavily with the do_wait code, I
was thinking too hard about the wrong thing and I now think I introduced a
bug whose inverse thought I was fixing.
Apparently noone was looking too hard over much shoulder, so as to cite my
bogus reasoning at the time. In the race condition when PTRACE_ATTACH is
about to steal a child and then the child hits a tracing event (what
my_ptrace_child checks for), the real parent does need to set its flag
noting it has some eligible live children. Otherwise a spurious ECHILD
error is possible, since the child in question is not yet on the
ptrace_children list.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The PF_DEAD setting doesn't belong to exit_notify(), move it to a proper
place.
Signed-off-by: Coywolf Qi Hunt <qiyong@fc-cn.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- Removes some trailing whitespace
- Breaks long lines and make other small changes to conform to CodingStyle
- Add explicit printk loglevels in two places.
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The attached patch gets rid of a "statement without effect" warning when
CONFIG_KEYS is disabled by making use of the return value of key_get().
The compiler will optimise all of this away when keys are disabled.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I could seldom reproduce a deadlock with a task not killable in T state
(TASK_STOPPED, not TASK_TRACED) by attaching a NPTL threaded program to
gdb, by segfaulting the task and triggering a core dump while some other
task is executing exit_group and while one task is in ptrace_attached
TASK_STOPPED state (not TASK_TRACED yet). This originated from a gdb
bugreport (the fact gdb was segfaulting the task wasn't a kernel bug), but
I just incidentally noticed the gdb bug triggered a real kernel bug as
well.
Most threads hangs in exit_mm because the core_dumping is still going, the
core dumping hangs because the stopped task doesn't exit, the stopped task
can't wakeup because it has SIGNAL_GROUP_EXIT set, hence the deadlock.
To me it seems that the problem is that the force_sig_specific(SIGKILL) in
zap_threads is a noop if the task has PF_PTRACED set (like in this case
because gdb is attached). The __ptrace_unlink does nothing because the
signal->flags is set to SIGNAL_GROUP_EXIT|SIGNAL_STOP_DEQUEUED (verified).
The above info also shows that the stopped task hit a race and got the stop
signal (presumably by the ptrace_attach, only the attach, state is still
TASK_STOPPED and gdb hangs waiting the core before it can set it to
TASK_TRACED) after one of the thread invoked the core dump (it's the core
dump that sets signal->flags to SIGNAL_GROUP_EXIT).
So beside the fact nobody would wakeup the task in __ptrace_unlink (the
state is _not_ TASK_TRACED), there's a secondary problem in the signal
handling code, where a task should ignore the ptrace-sigstops as long as
SIGNAL_GROUP_EXIT is set (or the wakeup in __ptrace_unlink path wouldn't be
enough).
So I attempted to make this patch that seems to fix the problem. There
were various ways to fix it, perhaps you prefer a different one, I just
opted to the one that looked safer to me.
I also removed the clearing of the stopped bits from the zap_other_threads
(zap_other_threads was safe unlike zap_threads). I don't like useless
code, this whole NPTL signal/ptrace thing is already unreadable enough and
full of corner cases without confusing useless code into it to make it even
less readable. And if this code is really needed, then you may want to
explain why it's not being done in the other paths that sets
SIGNAL_GROUP_EXIT at least.
Even after this patch I still wonder who serializes the read of
p->ptrace in zap_threads.
Patch is called ptrace-core_dump-exit_group-deadlock-1.
This was the trace I've got:
test T ffff81003e8118c0 0 14305 1 14311 14309 (NOTLB)
ffff810058ccdde8 0000000000000082 000001f4000037e1 ffff810000000013
00000000000000f8 ffff81003e811b00 ffff81003e8118c0 ffff810011362100
0000000000000012 ffff810017ca4180
Call Trace:<ffffffff801317ed>{try_to_wake_up+893} <ffffffff80141677>{finish_stop+87}
<ffffffff8014367f>{get_signal_to_deliver+1359} <ffffffff8010d3ad>{do_signal+157}
<ffffffff8013deee>{ptrace_check_attach+222} <ffffffff80111575>{sys_ptrace+2293}
<ffffffff80131810>{default_wake_function+0} <ffffffff80196399>{sys_ioctl+73}
<ffffffff8010dd27>{sysret_signal+28} <ffffffff8010e00f>{ptregscall_common+103}
test D ffff810011362100 0 14309 1 14305 14312 (NOTLB)
ffff810053c81cf8 0000000000000082 0000000000000286 0000000000000001
0000000000000195 ffff810011362340 ffff810011362100 ffff81002e338040
ffff810001e0ca80 0000000000000001
Call Trace:<ffffffff801317ed>{try_to_wake_up+893} <ffffffff8044677d>{wait_for_completion+173}
<ffffffff80131810>{default_wake_function+0} <ffffffff80137435>{exit_mm+149}
<ffffffff801381af>{do_exit+479} <ffffffff80138d0c>{do_group_exit+252}
<ffffffff801436db>{get_signal_to_deliver+1451} <ffffffff8010d3ad>{do_signal+157}
<ffffffff8013deee>{ptrace_check_attach+222} <ffffffff80140850>{specific_send_sig_info+2
<ffffffff8014208a>{force_sig_info+186} <ffffffff804479a0>{do_int3+112}
<ffffffff8010e308>{retint_signal+61}
test D ffff81002e338040 0 14311 1 14716 14305 (NOTLB)
ffff81005ca8dcf8 0000000000000082 0000000000000286 0000000000000001
0000000000000120 ffff81002e338280 ffff81002e338040 ffff8100481cb740
ffff810001e0ca80 0000000000000001
Call Trace:<ffffffff801317ed>{try_to_wake_up+893} <ffffffff8044677d>{wait_for_completion+173}
<ffffffff80131810>{default_wake_function+0} <ffffffff80137435>{exit_mm+149}
<ffffffff801381af>{do_exit+479} <ffffffff80142d0e>{__dequeue_signal+558}
<ffffffff80138d0c>{do_group_exit+252} <ffffffff801436db>{get_signal_to_deliver+1451}
<ffffffff8010d3ad>{do_signal+157} <ffffffff8013deee>{ptrace_check_attach+222}
<ffffffff80140850>{specific_send_sig_info+208} <ffffffff8014208a>{force_sig_info+186}
<ffffffff804479a0>{do_int3+112} <ffffffff8010e308>{retint_signal+61}
test D ffff810017ca4180 0 14312 1 14309 13882 (NOTLB)
ffff81005d15fcb8 0000000000000082 ffff81005d15fc58 ffffffff80130816
0000000000000897 ffff810017ca43c0 ffff810017ca4180 ffff81003e8118c0
0000000000000082 ffffffff801317ed
Call Trace:<ffffffff80130816>{activate_task+150} <ffffffff801317ed>{try_to_wake_up+893}
<ffffffff8044677d>{wait_for_completion+173} <ffffffff80131810>{default_wake_function+0}
<ffffffff8018cdc3>{do_coredump+819} <ffffffff80445f52>{thread_return+82}
<ffffffff801436d4>{get_signal_to_deliver+1444} <ffffffff8010d3ad>{do_signal+157}
<ffffffff8013deee>{ptrace_check_attach+222} <ffffffff80140850>{specific_send_sig_info+2
<ffffffff804472e5>{_spin_unlock_irqrestore+5} <ffffffff8014208a>{force_sig_info+186}
<ffffffff804476ff>{do_general_protection+159} <ffffffff8010e308>{retint_signal+61}
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch automatically updates a tasks NUMA mempolicy when its cpuset
memory placement changes. It does so within the context of the task,
without any need to support low level external mempolicy manipulation.
If a system is not using cpusets, or if running on a system with just the
root (all-encompassing) cpuset, then this remap is a no-op. Only when a
task is moved between cpusets, or a cpusets memory placement is changed
does the following apply. Otherwise, the main routine below,
rebind_policy() is not even called.
When mixing cpusets, scheduler affinity, and NUMA mempolicies, the
essential role of cpusets is to place jobs (several related tasks) on a set
of CPUs and Memory Nodes, the essential role of sched_setaffinity is to
manage a jobs processor placement within its allowed cpuset, and the
essential role of NUMA mempolicy (mbind, set_mempolicy) is to manage a jobs
memory placement within its allowed cpuset.
However, CPU affinity and NUMA memory placement are managed within the
kernel using absolute system wide numbering, not cpuset relative numbering.
This is ok until a job is migrated to a different cpuset, or what's the
same, a jobs cpuset is moved to different CPUs and Memory Nodes.
Then the CPU affinity and NUMA memory placement of the tasks in the job
need to be updated, to preserve their cpuset-relative position. This can
be done for CPU affinity using sched_setaffinity() from user code, as one
task can modify anothers CPU affinity. This cannot be done from an
external task for NUMA memory placement, as that can only be modified in
the context of the task using it.
However, it easy enough to remap a tasks NUMA mempolicy automatically when
a task is migrated, using the existing cpuset mechanism to trigger a
refresh of a tasks memory placement after its cpuset has changed. All that
is needed is the old and new nodemask, and notice to the task that it needs
to rebind its mempolicy. The tasks mems_allowed has the old mask, the
tasks cpuset has the new mask, and the existing
cpuset_update_current_mems_allowed() mechanism provides the notice. The
bitmap/cpumask/nodemask remap operators provide the cpuset relative
calculations.
This patch leaves open a couple of issues:
1) Updating vma and shmfs/tmpfs/hugetlbfs memory policies:
These mempolicies may reference nodes outside of those allowed to
the current task by its cpuset. Tasks are migrated as part of jobs,
which reside on what might be several cpusets in a subtree. When such
a job is migrated, all NUMA memory policy references to nodes within
that cpuset subtree should be translated, and references to any nodes
outside that subtree should be left untouched. A future patch will
provide the cpuset mechanism needed to mark such subtrees. With that
patch, we will be able to correctly migrate these other memory policies
across a job migration.
2) Updating cpuset, affinity and memory policies in user space:
This is harder. Any placement state stored in user space using
system-wide numbering will be invalidated across a migration. More
work will be required to provide user code with a migration-safe means
to manage its cpuset relative placement, while preserving the current
API's that pass system wide numbers, not cpuset relative numbers across
the kernel-user boundary.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add support for renaming cpusets. Only allow simple rename of cpuset
directories in place. Don't allow moving cpusets elsewhere in hierarchy or
renaming the special cpuset files in each cpuset directory.
The usefulness of this simple rename became apparent when developing task
migration facilities. It allows building a second cpuset hierarchy using
new names and containing new CPUs and Memory Nodes, moving tasks from the
old to the new cpusets, removing the old cpusets, and then renaming the new
cpusets to be just like the old names, so that any knowledge that the tasks
had of their cpuset names will still be valid.
Leaf node cpusets can be migrated to other CPUs or Memory Nodes by just
updating their 'cpus' and 'mems' files, but because no cpuset can contain
CPUs or Nodes not in its parent cpuset, one cannot do this in a cpuset
hierarchy without first expanding all the non-leaf cpusets to contain the
union of both the old and new CPUs and Nodes, which would obfuscate the
one-to-one migration of a task from one cpuset to another required to
correctly migrate the physical page frames currently allocated to that
task.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Overhaul cpuset locking. Replace single semaphore with two semaphores.
The suggestion to use two locks was made by Roman Zippel.
Both locks are global. Code that wants to modify cpusets must first
acquire the exclusive manage_sem, which allows them read-only access to
cpusets, and holds off other would-be modifiers. Before making actual
changes, the second semaphore, callback_sem must be acquired as well. Code
that needs only to query cpusets must acquire callback_sem, which is also a
global exclusive lock.
The earlier problems with double tripping are avoided, because it is
allowed for holders of manage_sem to nest the second callback_sem lock, and
only callback_sem is needed by code called from within __alloc_pages(),
where the double tripping had been possible.
This is not quite the same as a normal read/write semaphore, because
obtaining read-only access with intent to change must hold off other such
attempts, while allowing read-only access w/o such intention. Changing
cpusets involves several related checks and changes, which must be done
while allowing read-only queries (to avoid the double trip), but while
ensuring nothing changes (holding off other would be modifiers.)
This overhaul of cpuset locking also makes careful use of task_lock() to
guard access to the task->cpuset pointer, closing a couple of race
conditions noticed while reading this code (thanks, Roman). I've never
seen these races fail in any use or test.
See further the comments in the code.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove a rather hackish depth counter on cpuset locking. The depth counter
was avoiding a possible double trip on the global cpuset_sem semaphore. It
worked, but now an improved version of cpuset locking is available, to come
in the next patch, using two global semaphores.
This patch reverses "cpuset semaphore depth check deadlock fix"
The kernel still works, even after this patch, except for some rare and
difficult to reproduce race conditions when agressively creating and
destroying cpusets marked with the notify_on_release option, on very large
systems.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove one more useless line from cpuset_common_file_read().
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The majority of the sys_tkill() and sys_tgkill() function code is
duplicated between the two of them. This patch pulls the duplication out
into a separate function -- do_tkill() -- and lets sys_tkill() and
sys_tgkill() be simple wrappers around it. This should make it easier to
maintain in light of future changes.
Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This lock is used in sigqueue_free(), but it is always equal to
current->sighand->siglock, so we don't need to keep it in the struct
sigqueue.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove timer_list.magic and associated debugging code.
I originally added this when a spinlock was added to timer_list - this meant
that an all-zeroes timer became illegal and init_timer() was required.
That spinlock isn't even there any more, although timer.base must now be
initialised.
I'll keep this debugging code in -mm.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch makes the workqueus use alloc_percpu instead of an array. The
workqueues are placed on nodes local to each processor.
The workqueue structure can grow to a significant size on a system with
lots of processors if this patch is not applied. 64 bit architectures with
all debugging features enabled and configured for 512 processors will not
be able to boot without this patch.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Create a macro shift_right() that avoids the numerous ugly conditionals in the
NTP code that look like:
if(a < 0)
b = -(-a >> shift);
else
b = a >> shift;
Replacing it with:
b = shift_right(a, shift);
This should have zero effect on the logic, however it should probably have
a bit of testing just to be sure.
Also replace open-coded min/max with the macros.
Signed-off-by : John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Enhance the kthread API by adding kthread_stop_sem, for use in stopping
threads that spend their idle time waiting on a semaphore.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Every user of init_timer() also needs to initialize ->function and ->data
fields. This patch adds a simple setup_timer() helper for that.
The schedule_timeout() is patched as an example of usage.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add pm_ops.valid callback, so only the available pm states show in
/sys/power/state. And this also makes an earlier states error report at
enter_state before we do actual suspend/resume.
Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Acked-by: Pavel Machek<pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch simplifies the progress meter in disk.c:free_some_memory()
and makes disk.c:pm_suspend_disk() call device_resume() explicitly in the
suspend path.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch merges two functions in a trivial way.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Reduce number of ifdefs somehow, and fix whitespace a bit. No real code
changes.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch makes swsusp use the PG_nosave and PG_nosave_free flags to
mark pages that should be freed in case of an error during resume.
This allows us to simplify the code and to use swsusp_free() in all of the
swsusp's resume error paths, which makes them actually work.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch moves the functionality of swsusp related to creating and
handling the snapshot of memory to a separate file, snapshot.c
This should enable us to untangle the code in the future and eventually to
implement some parts of swsusp.c in the user space.
The patch does not change the code.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch makes swsusp use PG_nosave and PG_nosave_free flags to
mark pages that should be freed after the state of the system has been
restored from the image (or in case of an error during suspend).
This allows us to avoid storing metadata in swap twice and to reduce the
amount of memory needed by swsusp. Additionally, it allows us to simplify
the code by removing a couple of functions that are no longer necessary.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
cpufreq entries in sysfs should only be populated when CPU is online state.
When we either boot with maxcpus=x and then boot the other cpus by echoing
to sysfs online file, these entries should be created and destroyed when
CPU_DEAD is notified. Same treatement as cache entries under sysfs.
We place the processor in the lowest frequency, so hw managed P-State
transitions can still work on the other threads to save power.
Primary goal was to just make these directories appear/disapper dynamically.
There is one in this patch i had to do, which i really dont like myself but
probably best if someone handling the cpufreq infrastructure could give
this code right treatment if this is not acceptable. I guess its probably
good for the first cut.
- Converting lock_cpu_hotplug()/unlock_cpu_hotplug() to disable/enable preempt.
The locking was smack in the middle of the notification path, when the
hotplug is already holding the lock. I tried another solution to avoid this
so avoid taking locks if we know we are from notification path. The solution
was getting very ugly and i decided this was probably good for this iteration
until someone who understands cpufreq could do a better job than me.
(akpm: export cpucontrol to GPL modules: drivers/cpufreq/cpufreq_stats.c now
does lock_cpu_hotplug())
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Zwane Mwaikambo <zwane@holomorphy.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Since CONFIG_IKCONFIG_PROC already depends on CONFIG_IKCONFIG, adding
configs.o again is redundant.
Signed-off-by: Brian Gerst <bgerst@didntduck.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with
a many-threaded application which concurrently initializes different parts of
a large anonymous area.
This patch corrects that, by using a separate spinlock per page table page, to
guard the page table entries in that page, instead of using the mm's single
page_table_lock. (But even then, page_table_lock is still used to guard page
table allocation, and anon_vma allocation.)
In this implementation, the spinlock is tucked inside the struct page of the
page table page: with a BUILD_BUG_ON in case it overflows - which it would in
the case of 32-bit PA-RISC with spinlock debugging enabled.
Splitting the lock is not quite for free: another cacheline access. Ideally,
I suppose we would use split ptlock only for multi-threaded processes on
multi-cpu machines; but deciding that dynamically would have its own costs.
So for now enable it by config, at some number of cpus - since the Kconfig
language doesn't support inequalities, let preprocessor compare that with
NR_CPUS. But I don't think it's worth being user-configurable: for good
testing of both split and unsplit configs, split now at 4 cpus, and perhaps
change that to 8 later.
There is a benefit even for singly threaded processes: kswapd can be attacking
one part of the mm while another part is busy faulting.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Final step in pushing down common core's page_table_lock. follow_page no
longer wants caller to hold page_table_lock, uses pte_offset_map_lock itself;
and so no page_table_lock is taken in get_user_pages itself.
But get_user_pages (and get_futex_key) do then need follow_page to pin the
page for them: take Daniel's suggestion of bitflags to follow_page.
Need one for WRITE, another for TOUCH (it was the accessed flag before:
vanished along with check_user_page_readable, but surely get_numa_maps is
wrong to mark every page it finds as accessed), another for GET.
And another, ANON to dispose of untouched_anonymous_page: it seems silly for
that to descend a second time, let follow_page observe if there was no page
table and return ZERO_PAGE if so. Fix minor bug in that: check VM_LOCKED -
make_pages_present ought to make readonly anonymous present.
Give get_numa_maps a cond_resched while we're there.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Second step in pushing down the page_table_lock. Remove the temporary
bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not
to hold page_table_lock, whether it's on init_mm or a user mm; take
page_table_lock internally to check if a racing task already allocated.
Convert their callers from common code. But avoid coming back to change them
again later: instead of moving the spin_lock(&mm->page_table_lock) down,
switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which
encapsulate the mapping+locking and unlocking+unmapping together, and in the
end may use alternatives to the mm page_table_lock itself.
These callers all hold mmap_sem (some exclusively, some not), so at no level
can a page table be whipped away from beneath them; and pte_alloc uses the
"atomic" pmd_present to test whether it needs to allocate. It appears that on
all arches we can safely descend without page_table_lock.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
update_mem_hiwater has attracted various criticisms, in particular from those
concerned with mm scalability. Originally it was called whenever rss or
total_vm got raised. Then many of those callsites were replaced by a timer
tick call from account_system_time. Now Frank van Maarseveen reports that to
be found inadequate. How about this? Works for Frank.
Replace update_mem_hiwater, a poor combination of two unrelated ops, by macros
update_hiwater_rss and update_hiwater_vm. Don't attempt to keep
mm->hiwater_rss up to date at timer tick, nor every time we raise rss (usually
by 1): those are hot paths. Do the opposite, update only when about to lower
rss (usually by many), or just before final accounting in do_exit. Handle
mm->hiwater_vm in the same way, though it's much less of an issue. Demand
that whoever collects these hiwater statistics do the work of taking the
maximum with rss or total_vm.
And there has been no collector of these hiwater statistics in the tree. The
new convention needs an example, so match Frank's usage by adding a VmPeak
line above VmSize to /proc/<pid>/status, and also a VmHWM line above VmRSS
(High-Water-Mark or High-Water-Memory).
There was a particular anomaly during mremap move, that hiwater_vm might be
captured too high. A fleeting such anomaly remains, but it's quickly
corrected now, whereas before it would stick.
What locking? None: if the app is racy then these statistics will be racy,
it's not worth any overhead to make them exact. But whenever it suits,
hiwater_vm is updated under exclusive mmap_sem, and hiwater_rss under
page_table_lock (for now) or with preemption disabled (later on): without
going to any trouble, minimize the time between reading current values and
updating, to minimize those occasions when a racing thread bumps a count up
and back down in between.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove PageReserved() calls from core code by tightening VM_RESERVED
handling in mm/ to cover PageReserved functionality.
PageReserved special casing is removed from get_page and put_page.
All setting and clearing of PageReserved is retained, and it is now flagged
in the page_alloc checks to help ensure we don't introduce any refcount
based freeing of Reserved pages.
MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being
deprecated. We never completely handled it correctly anyway, and is be
reintroduced in future if required (Hugh has a proof of concept).
Once PageReserved() calls are removed from kernel/power/swsusp.c, and all
arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can
be trivially removed.
Last real user of PageReserved is swsusp, which uses PageReserved to
determine whether a struct page points to valid memory or not. This still
needs to be addressed (a generic page_is_ram() should work).
A last caveat: the ZERO_PAGE is now refcounted and managed with rmap (and
thus mapcounted and count towards shared rss). These writes to the struct
page could cause excessive cacheline bouncing on big systems. There are a
number of ways this could be addressed if it is an issue.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Refcount bug fix for filemap_xip.c
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
One anomaly remains from when Andrea rationalized the responsibilities of
mmap_sem and page_table_lock: in dup_mmap we add vmas to the child holding its
page_table_lock, but not the mmap_sem which normally guards the vma list and
rbtree. Which could be an issue for unuse_mm: though since it just walks down
the list (today with page_table_lock, tomorrow not), it's probably okay. Will
need a memory barrier? Oh, keep it simple, Nick and I agreed, no harm in
taking child's mmap_sem here.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use the parent's oldmm throughout dup_mmap, instead of perversely going back
to current->mm. (Can you hear the sigh of relief from those mpnts? Usually I
squash them, but not today.)
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I was lazy when we added anon_rss, and chose to change as few places as
possible. So currently each anonymous page has to be counted twice, in rss
and in anon_rss. Which won't be so good if those are atomic counts in some
configurations.
Change that around: keep file_rss and anon_rss separately, and add them
together (with get_mm_rss macro) when the total is needed - reading two
atomics is much cheaper than updating two atomics. And update anon_rss
upfront, typically in memory.c, not tucked away in page_add_anon_rmap.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
How is anon_rss initialized? In dup_mmap, and by mm_alloc's memset; but
that's not so good if an mm_counter_t is a special type. And how is rss
initialized? By set_mm_counter, all over the place. Come on, we just need to
initialize them both at once by set_mm_counter in mm_init (which follows the
memcpy when forking).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The original vm_stat_account has fallen into disuse, with only one user, and
only one user of vm_stat_unaccount. It's easier to keep track if we convert
them all to __vm_stat_account, then free it from its __shackles.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
frv, sh64, ia64 and sparc64 do not have do_settimeofday() exported (the
last two are using variant in kernel/time.c). Exports added to match
the rest of architectures.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
exit_signal() (called from copy_process's error path) should decrement
->signal->live, otherwise forking process will miss 'group_dead' in
do_exit().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This just makes sure that a thread's expiry times can't get reset after
it clears them in do_exit.
This is what allowed us to re-introduce the stricter BUG_ON() check in
a362f463a6.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This reverts commit 3de463c7d9.
Roland has another patch that allows us to leave the BUG_ON() in place
by just making sure that the condition it tests for really is always
true.
That goes in next.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There's a silly off-by-one error in the code that updates the expiration
of posix CPU timers, causing them to not be properly updated when they
hit exactly on their expiration time (which should be the normal case).
This causes them to then fire immediately again, and only _then_ get
properly updated.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
With CONFIG_SMP=n:
*** Warning: "cpu_online_map" [drivers/firmware/dcdbas.ko] undefined!
due to set_cpus_allowed().
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This might be harmless, but looks like a race from code inspection (I
was unable to trigger it). I must admit, I don't understand why we
can't return TIMER_RETRY after 'spin_unlock(&p->sighand->siglock)'
without doing bump_cpu_timer(), but this is what original code does.
posix_cpu_timer_set:
read_lock(&tasklist_lock);
spin_lock(&p->sighand->siglock);
list_del_init(&timer->it.cpu.entry);
spin_unlock(&p->sighand->siglock);
We are probaly deleting the timer from run_posix_cpu_timers's 'firing'
local list_head while run_posix_cpu_timers() does list_for_each_safe.
Various bad things can happen, for example we can just delete this timer
so that list_for_each() will not notice it and run_posix_cpu_timers()
will not reset '->firing' flag. In that case,
....
if (timer->it.cpu.firing) {
read_unlock(&tasklist_lock);
timer->it.cpu.firing = -1;
return TIMER_RETRY;
}
sys_timer_settime() goes to 'retry:', calls posix_cpu_timer_set() again,
it returns TIMER_RETRY ...
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
do_exit() clears ->it_##clock##_expires, but nothing prevents
another cpu to attach the timer to exiting process after that.
After exit_notify() does 'write_unlock_irq(&tasklist_lock)' and
before do_exit() calls 'schedule() local timer interrupt can find
tsk->exit_state != 0. If that state was EXIT_DEAD (or another cpu
does sys_wait4) interrupted task has ->signal == NULL.
At this moment exiting task has no pending cpu timers, they were cleaned
up in __exit_signal()->posix_cpu_timers_exit{,_group}(), so we can just
return from irq.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1. cleanup_timers() sets timer->task = NULL under tasklist + ->sighand locks.
That means that this code in posix_cpu_timer_del() and posix_cpu_timer_set()
lock_timer(timer);
if (timer->task == NULL)
return;
read_lock(tasklist);
put_task_struct(timer->task)
is racy. With this patch timer->task modified and accounted only under
timer->it_lock. Sadly, this means that dead task_struct won't be freed
until timer deleted or armed.
2. run_posix_cpu_timers() collects expired timers into local list under
tasklist + ->sighand again. That means that posix_cpu_timer_del()
should check timer->it.cpu.firing under these locks too.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Bursty timers aren't good for anybody, very much including latency for
other programs when we trigger lots of timers in interrupt context. So
set a random limit, after which we'll handle the rest on the next timer
tick.
Noted by Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When I originally moved exit_itimers into __exit_signal, that was the only
place where we could reliably know it was the last thread in the group
dying, without races. Since then we've gotten the signal_struct.live
counter, and do_exit can reliably do group-wide cleanup work.
This patch moves the call to do_exit, where it's made without locks. This
avoids the deadlock issues that the old __exit_signal code's comment talks
about, and the one that Oleg found recently with process CPU timers.
[ This replaces e03d13e985, which is why
it was just reverted. ]
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The PF_NOFREEZE process flag should not be inherited when a thread is
forked. This patch (as585) removes the flag from the child.
This problem is starting to show up more and more as drivers turn to the
kthread API instead of using kernel_thread(). As a result, their kernel
threads are now children of the kthread worker instead of modprobe, and
they inherit the PF_NOFREEZE flag. This can cause problems during system
suspend; the kernel threads are not getting frozen as they ought to be.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Oleg Nesterov reported an SMP deadlock. If there is a running timer
tracking a different process's CPU time clock when the process owning
the timer exits, we deadlock on tasklist_lock in posix_cpu_timer_del via
exit_itimers.
That code was using tasklist_lock to check for a race with __exit_signal
being called on the timer-target task and clearing its ->signal.
However, there is actually no such race. __exit_signal will have called
posix_cpu_timers_exit and posix_cpu_timers_exit_group before it does
that. Those will clear those k_itimer's association with the dying
task, so posix_cpu_timer_del will return early and never reach the code
in question.
In addition, posix_cpu_timer_del called from exit_itimers during execve
or directly from timer_delete in the process owning the timer can race
with an exiting timer-target task to cause a double put on timer-target
task struct. Make sure we always access cpu_timers lists with sighand
lock held.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This makes call_rcu() keep track of how many events there are on the RCU
list, and cause a reschedule event when the list gets too long.
This helps keep RCU event lists down.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make sure we release the task struct properly when releasing pending
timers.
release_task() does write_lock_irq(&tasklist_lock), so it can't race
with run_posix_cpu_timers() on any cpu.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Dipankar made RCU limit the batch size to improve latency, but that
approach is unworkable: it can cause the RCU queues to grow without
bounds, since the batch limiter ended up limiting the callbacks.
So make the limit much higher, and start planning on instead limiting
the batch size by doing RCU callbacks more often if the queue looks like
it might be growing too long.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Adds the missing EXPORT_SYMBOL_GPL for getnstimeofday() when
CONFIG_TIME_INTERPOLATION isn't set. Needed by drivers/char/mmtimer.c
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If a process issues an URB from userspace and (starts to) terminate
before the URB comes back, we run into the issue described above. This
is because the urb saves a pointer to "current" when it is posted to the
device, but there's no guarantee that this pointer is still valid
afterwards.
In fact, there are three separate issues:
1) the pointer to "current" can become invalid, since the task could be
completely gone when the URB completion comes back from the device.
2) Even if the saved task pointer is still pointing to a valid task_struct,
task_struct->sighand could have gone meanwhile.
3) Even if the process is perfectly fine, permissions may have changed,
and we can no longer send it a signal.
So what we do instead, is to save the PID and uid's of the process, and
introduce a new kill_proc_info_as_uid() function.
Signed-off-by: Harald Welte <laforge@gnumonks.org>
[ Fixed up types and added symbol exports ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch makes swsusp avoid the possible temporary corruption
of page translation tables during resume on x86-64. This is achieved by
creating a copy of the relevant page tables that will not be modified by
swsusp and can be safely used by it on resume.
The problem is that during resume on x86-64 swsusp may temporarily
corrupt the page tables used for the direct mapping of RAM. If that
happens, a page fault occurs and cannot be handled properly, which leads
to the solid hang of the affected system. This leads to the loss of the
system's state from before suspend and may result in the loss of data or
the corruption of filesystems, so it is a serious issue. Also, it
appears to happen quite often (for me, as often as 50% of the time).
The problem is related to the fact that (at least) one of the PMD
entries used in the direct memory mapping (starting at PAGE_OFFSET)
points to a page table the physical address of which is much greater
than the physical address of the PMD entry itself. Moreover,
unfortunately, the physical address of the page table before suspend
(i.e. the one stored in the suspend image) happens to be different to
the physical address of the corresponding page table used during resume
(i.e. the one that is valid right before swsusp_arch_resume() in
arch/x86_64/kernel/suspend_asm.S is executed). Thus while the image is
restored, the "offending" PMD entry gets overwritten, so it does not
point to the right physical address any more (i.e. there's no page
table at the address pointed to by it, because it points to the address
the page table has been at during suspend). Consequently, if the PMD
entry is used later on, and it _is_ used in the process of copying the
image pages, a page fault occurs, but it cannot be handled in the normal
way and the system hangs.
In principle we can call create_resume_mapping() from
swsusp_arch_resume() (ie. from suspend_asm.S), but then the memory
allocations in create_resume_mapping(), resume_pud_mapping(), and
resume_pmd_mapping() must be made carefully so that we use _only_
NosaveFree pages in them (the other pages are overwritten by the loop in
swsusp_arch_resume()). Additionally, we are in atomic context at that
time, so we cannot use GFP_KERNEL. Moreover, if one of the allocations
fails, we should free all of the allocated pages, so we need to trace
them somehow.
All of this is done in the appended patch, except that the functions
populating the page tables are located in arch/x86_64/kernel/suspend.c
rather than in init.c. It may be done in a more elegan way in the
future, with the help of some swsusp patches that are in the works now.
[AK: move some externs into headers, renamed a function]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- added typedef unsigned int __nocast gfp_t;
- replaced __nocast uses for gfp flags with gfp_t - it gives exactly
the same warnings as far as sparse is concerned, doesn't change
generated code (from gcc point of view we replaced unsigned int with
typedef) and documents what's going on far better.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Let's suppose we have 2 threads in thread group:
A - does coredump
B - has pending SIGSTOP
thread A thread B
do_coredump: get_signal_to_deliver:
lock(->sighand)
->signal->flags = SIGNAL_GROUP_EXIT
unlock(->sighand)
lock(->sighand)
signr = dequeue_signal()
->signal->flags |= SIGNAL_STOP_DEQUEUED
return SIGSTOP;
do_signal_stop:
unlock(->sighand)
coredump_wait:
zap_threads:
lock(tasklist_lock)
send SIGKILL to B
// signal_wake_up() does nothing
unlock(tasklist_lock)
lock(tasklist_lock)
lock(->sighand)
re-check sig->flags & SIGNAL_STOP_DEQUEUED, yes
set_current_state(TASK_STOPPED);
finish_stop:
schedule();
// ->state == TASK_STOPPED
wait_for_completion(&startup_done)
// waits for complete() from B,
// ->state == TASK_UNINTERRUPTIBLE
We can't wake up 'B' in any way:
SIGCONT will be ignored because handle_stop_signal() sees
->signal->flags & SIGNAL_GROUP_EXIT.
sys_kill(SIGKILL)->__group_complete_signal() will choose
uninterruptible 'A', so it can't help.
sys_tkill(B, SIGKILL) will be ignored by specific_send_sig_info()
because B already has pending SIGKILL.
This scenario is not possbile if 'A' does do_group_exit(), because
it sets sig->flags = SIGNAL_GROUP_EXIT and delivers SIGKILL to
subthreads atomically, holding both tasklist_lock and sighand->lock.
That means that do_signal_stop() will notice !SIGNAL_STOP_DEQUEUED
after re-locking ->sighand. And it is not possible to any other
thread to re-add SIGNAL_STOP_DEQUEUED later, because dequeue_signal()
can only return SIGKILL.
I think it is better to change do_coredump() to do sigaddset(SIGKILL)
and signal_wake_up() under sighand->lock, but this patch is much
simpler.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We should always use bitmask ops, rather than depend on some ordering of
the different states. With the TASK_NONINTERACTIVE flag, the inequality
doesn't really work.
Oleg Nesterov argues (likely correctly) that this test is unnecessary in
the first place. However, the minimal fix for now is to at least make
it work in the presense of TASK_NONINTERACTIVE. Waiting for consensus
from Roland & co on potential bigger cleanups.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Switched cpuset_common_file_read() to simple_read_from_buffer(), killed
a bunch of useless (and not quite correct - e.g. min(size_t,ssize_t))
code.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Any tests using < TASK_STOPPED or the like are left over from the time
when the TASK_ZOMBIE and TASK_DEAD bits were in the same word, and it
served to check for "stopped or dead". I think this one in
do_signal_stop is the only such case. It has been buggy ever since
exit_state was separated, and isn't testing the exit_state value.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Don't leak a page of memory if user reads a cpuset file past eof.
Signed-off-by: KUROSAWA Takahiro <kurosawa@valinux.co.jp>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch makes swsusp avoid problems during resume if there are
too many pages to save on suspend. It adds a constant that allows us to
verify if we are going to save too many pages and implements the check
(this is done as early as we can tell that the check will trigger, which is
in swsusp_alloc()).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Dave Jones says:
... if the modprobe.conf has trailing whitespace, modules fail to load
with the following helpful message..
snd_intel8x0: Unknown parameter `'
Previous version truncated last argument.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Prevent swsusp from leaking some memory in case of an error in
read_pagedir(). It also prevents the BUG_ON() from triggering if there's
an error while reading swap.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch removes some wrong code from the data_free() function
in swsusp.
This function could only be called if there's an error while writing the
suspend image to swap, so it is not triggered easily. However, if
triggered, it would probably corrupt some memory.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Some IRQ controllers don't need an ack function (e.g. OpenPIC on
PPC platforms) and for them we'd rather not have the overhead
of doing an indirect call to a function that does nothing.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Bhavesh P. Davda <bhavesh@avaya.com> noticed that SIGKILL wouldn't
properly kill a process under just the right cicumstances: a stopped
task that already had another signal queued would get the SIGKILL
queued onto the shared queue, and there it would remain until SIGCONT.
This simplifies the signal acceptance logic, and fixes the bug in the
process.
Losely based on an earlier patch by Bhavesh.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The following patch makes swsusp avoid triggering the BUG_ON() in
swsusp_suspend() if there is not enough memory for suspend.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In the lead up to 2.6.13 I fixed a large number of reboot problems by
making the calling conventions consistent. Despite checking and double
checking my work it appears I missed an obvious one.
The S4 suspend code for PM_DISK_PLATFORM was also calling device_shutdown
without setting system_state, and was not calling the appropriate
reboot_notifier.
This patch fixes the bug by replacing the call of device_suspend with
kernel_poweroff_prepare.
Various forms of this failure have been fixed and tracked for a while.
Thanks for tracking this down go to: Alexey Starikovskiy, Meelis Roos
<mroos@linux.ee>, Nigel Cunningham <ncunningham@cyclades.com>, Pierre
Ossman <drzeus-list@drzeus.cx>
History of this bug is at:
http://bugme.osdl.org/show_bug.cgi?id=4320
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In the lead up to 2.6.13 I fixed a large number of reboot problems by
making the calling conventions consistent. Despite checking and double
checking my work it appears I missed an obvious one.
This first patch simply refactors the reboot routines so all of the
preparation for various kinds of reboots are in their own functions.
Making it very hard to get the various kinds of reboot out of sync.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
ia64's sched_clock() accesses per-cpu data which isn't set up at boot time.
Hence ia64 cannot use printk timestamping, because printk() will crash in
sched_clock().
So make printk() use printk_clock(), defaulting to sched_clock(), overrideable
by the architecture via attribute(weak).
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
With the new fdtable locking rules, you have to protect fdtable with either
->file_lock or rcu_read_lock/unlock(). There are some places where we
aren't doing either. This patch fixes those places.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2.6.13 incorporated Alan Cox's patch for /proc/sys/fs/suid_dumpable (one
version of this patch can be found here
http://marc.theaimsgroup.com/?l=linux-kernel&m=109647550421014&w=2 ).
This patch also made corresponding changes in kernel/sys.c to change the
prctl() PR_SET_DUMPABLE operation so that the permitted range of 'arg2' was
modified from 0..1 to 0..2.
However, a corresponding change was not made for PR_GET_DUMPABLE: if the
dumpable flag is non-zero, then PR_GET_DUMPABLE always returns 1, so that
the caller can't determine the true setting of this flag.
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix a problem wherein a new-born task is added to a dead CPU.
Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
fix up the runqueue lock owner only if we truly did a context-switch
with the runqueue lock held. Impacts ia64, mips, sparc64 and arm.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use the add_taint() interface for setting tainted bit flags instead of
doing it manually.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
These functions don't need schedule_timeout()'s barrier.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Optimize the deadlock avoidance check on the global cpuset
semaphore cpuset_sem. Instead of adding a depth counter to the
task struct of each task, rather just two words are enough, one
to store the depth and the other the current cpuset_sem holder.
Thanks to Nikita Danilov for the idea.
Signed-off-by: Paul Jackson <pj@sgi.com>
[ We may want to change this further, but at least it's now
a totally internal decision to the cpusets code ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
..and only enable them for ia64. The functions are only valid
when the whole system has been totally stopped and no scheduler
activity is ongoing on any CPU, and interrupts are globally
disabled.
In other words, they aren't useful for anything else. So make
sure that nobody can use them by mistake.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Scheduler hooks to see/change which process is deemed to be on a cpu.
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Add schedule_timeout_{,un}interruptible() interfaces so that
schedule_timeout() callers don't have to worry about forgetting to add the
set_current_state() call beforehand.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Don't pull tasks from a group if that would cause the group's total load to
drop below its total cpu_power (ie. cause the group to start going idle).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Jack Steiner brought this issue at my OLS talk.
Take a scenario where two tasks are pinned to two HT threads in a physical
package. Idle packages in the system will keep kicking migration_thread on
the busy package with out any success.
We will run into similar scenarios in the presence of CMP/NUMA.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In sys_sched_yield(), we cache current->array in the "array" variable, thus
there's no need to dereference "current" again later.
Signed-Off-By: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If an idle sibling of an HT queue encounters a busy sibling, then make
higher level load balancing of the non-idle variety.
Performance of multiprocessor HT systems with low numbers of tasks
(generally < number of virtual CPUs) can be significantly worse than the
exact same workloads when running in non-HT mode. The reason is largely
due to poor scheduling behaviour.
This patch improves the situation, making the performance gap far less
significant on one problematic test case (tbench).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
During periodic load balancing, don't hold this runqueue's lock while
scanning remote runqueues, which can take a non trivial amount of time
especially on very large systems.
Holding the runqueue lock will only help to stabilise ->nr_running, however
this doesn't do much to help because tasks being woken will simply get held
up on the runqueue lock, so ->nr_running would not provide a really
accurate picture of runqueue load in that case anyway.
What's more, ->nr_running (and possibly the cpu_load averages) of remote
runqueues won't be stable anyway, so load balancing is always an inexact
operation.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Similarly to the earlier change in load_balance, only lock the runqueue in
load_balance_newidle if the busiest queue found has a nr_running > 1. This
will reduce frequency of expensive remote runqueue lock aquisitions in the
schedule() path on some workloads.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
William Weston reported unusually high scheduling latencies on his x86 HT
box, on the -RT kernel. I managed to reproduce it on my HT box and the
latency tracer shows the incident in action:
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
du-2803 3Dnh2 0us : __trace_start_sched_wakeup (try_to_wake_up)
..............................................................
... we are running on CPU#3, PID 2778 gets woken to CPU#1: ...
..............................................................
du-2803 3Dnh2 0us : __trace_start_sched_wakeup <<...>-2778> (73 1)
du-2803 3Dnh2 0us : _raw_spin_unlock (try_to_wake_up)
................................................
... still on CPU#3, we send an IPI to CPU#1: ...
................................................
du-2803 3Dnh1 0us : resched_task (try_to_wake_up)
du-2803 3Dnh1 1us : smp_send_reschedule (try_to_wake_up)
du-2803 3Dnh1 1us : send_IPI_mask_bitmask (smp_send_reschedule)
du-2803 3Dnh1 2us : _raw_spin_unlock_irqrestore (try_to_wake_up)
...............................................
... 1 usec later, the IPI arrives on CPU#1: ...
...............................................
<idle>-0 1Dnh. 2us : smp_reschedule_interrupt (c0100c5a 0 0)
So far so good, this is the normal wakeup/preemption mechanism. But here
comes the scheduler anomaly on CPU#1:
<idle>-0 1Dnh. 2us : preempt_schedule_irq (need_resched)
<idle>-0 1Dnh. 2us : preempt_schedule_irq (need_resched)
<idle>-0 1Dnh. 3us : __schedule (preempt_schedule_irq)
<idle>-0 1Dnh. 3us : profile_hit (__schedule)
<idle>-0 1Dnh1 3us : sched_clock (__schedule)
<idle>-0 1Dnh1 4us : _raw_spin_lock_irq (__schedule)
<idle>-0 1Dnh1 4us : _raw_spin_lock_irqsave (__schedule)
<idle>-0 1Dnh2 5us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh1 5us : preempt_schedule (__schedule)
<idle>-0 1Dnh1 6us : _raw_spin_lock (__schedule)
<idle>-0 1Dnh2 6us : find_next_bit (__schedule)
<idle>-0 1Dnh2 6us : _raw_spin_lock (__schedule)
<idle>-0 1Dnh3 7us : find_next_bit (__schedule)
<idle>-0 1Dnh3 7us : find_next_bit (__schedule)
<idle>-0 1Dnh3 8us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh2 8us : preempt_schedule (__schedule)
<idle>-0 1Dnh2 8us : find_next_bit (__schedule)
<idle>-0 1Dnh2 9us : trace_stop_sched_switched (__schedule)
<idle>-0 1Dnh2 9us : _raw_spin_lock (trace_stop_sched_switched)
<idle>-0 1Dnh3 10us : trace_stop_sched_switched <<...>-2778> (73 8c)
<idle>-0 1Dnh3 10us : _raw_spin_unlock (trace_stop_sched_switched)
<idle>-0 1Dnh1 10us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh. 11us : local_irq_enable_noresched (preempt_schedule_irq)
<idle>-0 1Dnh. 11us < (0)
we didnt pick up pid 2778! It only gets scheduled much later:
<...>-2778 1Dnh2 412us : __switch_to (__schedule)
<...>-2778 1Dnh2 413us : __schedule <<idle>-0> (8c 73)
<...>-2778 1Dnh2 413us : _raw_spin_unlock (__schedule)
<...>-2778 1Dnh1 413us : trace_stop_sched_switched (__schedule)
<...>-2778 1Dnh1 414us : _raw_spin_lock (trace_stop_sched_switched)
<...>-2778 1Dnh2 414us : trace_stop_sched_switched <<...>-2778> (73 1)
<...>-2778 1Dnh2 414us : _raw_spin_unlock (trace_stop_sched_switched)
<...>-2778 1Dnh1 415us : trace_stop_sched_switched (__schedule)
the reason for this anomaly is the following code in dependent_sleeper():
/*
* If a user task with lower static priority than the
* running task on the SMT sibling is trying to schedule,
* delay it till there is proportionately less timeslice
* left of the sibling task to prevent a lower priority
* task from using an unfair proportion of the
* physical cpu's resources. -ck
*/
[...]
if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) /
100) > task_timeslice(p)))
ret = 1;
Note that in contrast to the comment above, we dont actually do the check
based on static priority, we do the check based on timeslices. But
timeslices go up and down, and even highprio tasks can randomly have very
low timeslices (just before their next refill) and can thus be judged as
'lowprio' by the above piece of code. This condition is clearly buggy.
The correct test is to check for static_prio _and_ to check for the
preemption priority. Even on different static priority levels, a
higher-prio interactive task should not be delayed due to a
higher-static-prio CPU hog.
There is a symmetric bug in the 'kick SMT sibling' code of this function as
well, which can be solved in a similar way.
The patch below (against the current scheduler queue in -mm) fixes both
bugs. I have build and boot-tested this on x86 SMT, and nice +20 tasks
still get properly throttled - so the dependent-sleeper logic is still in
action.
btw., these bugs pessimised the SMT scheduler because the 'delay wakeup'
property was applied too liberally, so this fix is likely a throughput
improvement as well.
I separated out a smt_slice() function to make the code easier to read.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch implements a task state bit (TASK_NONINTERACTIVE), which can be
used by blocking points to mark the task's wait as "non-interactive". This
does not mean the task will be considered a CPU-hog - the wait will simply
not have an effect on the waiting task's priority - positive or negative
alike. Right now only pipe_wait() will make use of it, because it's a
common source of not-so-interactive waits (kernel compilation jobs, etc.).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add relevant checks into find_idlest_group() and find_idlest_cpu() to make
them return only the groups that have allowed CPUs and allowed CPUs
respectively.
Signed-off-by: M.Baris Demiray <baris@labristeknoloji.com>
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The hyperthread aware nice handling currently puts to sleep any non real
time task when a real time task is running on its sibling cpu. This can
lead to prolonged starvation by having the non real time task pegged to the
cpu with load balancing not pulling that task away.
Currently we force lower priority hyperthread tasks to run a percentage of
time difference based on timeslice differences which is meaningless when
comparing real time tasks to SCHED_NORMAL tasks. We can allow non real
time tasks to run with real time tasks on the sibling up to per_cpu_gain%
if we use jiffies as a counter.
Cleanups and micro-optimisations to the relevant code section should make
it more understandable as well.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The cpusets-formalize-intermediate-gfp_kernel-containment patch
has a deadlock problem.
This patch was part of a set of four patches to make more
extensive use of the cpuset 'mem_exclusive' attribute to
manage kernel GFP_KERNEL memory allocations and to constrain
the out-of-memory (oom) killer.
A task that is changing cpusets in particular ways on a system
when it is very short of free memory could double trip over
the global cpuset_sem semaphore (get the lock and then deadlock
trying to get it again).
The second attempt to get cpuset_sem would be in the routine
cpuset_zone_allowed(). This was discovered by code inspection.
I can not reproduce the problem except with an artifically
hacked kernel and a specialized stress test.
In real life you cannot hit this unless you are manipulating
cpusets, and are very unlikely to hit it unless you are rapidly
modifying cpusets on a memory tight system. Even then it would
be a rare occurence.
If you did hit it, the task double tripping over cpuset_sem
would deadlock in the kernel, and any other task also trying
to manipulate cpusets would deadlock there too, on cpuset_sem.
Your batch manager would be wedged solid (if it was cpuset
savvy), but classic Unix shells and utilities would work well
enough to reboot the system.
The unusual condition that led to this bug is that unlike most
semaphores, cpuset_sem _can_ be acquired while in the page
allocation code, when __alloc_pages() calls cpuset_zone_allowed.
So it easy to mistakenly perform the following sequence:
1) task makes system call to alter a cpuset
2) take cpuset_sem
3) try to allocate memory
4) memory allocator, via cpuset_zone_allowed, trys to take cpuset_sem
5) deadlock
The reason that this is not a serious bug for most users
is that almost all calls to allocate memory don't require
taking cpuset_sem. Only some code paths off the beaten
track require taking cpuset_sem -- which is good. Taking
a global semaphore on the main code path for allocating
memory would not scale well.
This patch fixes this deadlock by wrapping the up() and down()
calls on cpuset_sem in kernel/cpuset.c with code that tracks
the nesting depth of the current task on that semaphore, and
only does the real down() if the task doesn't hold the lock
already, and only does the real up() if the nesting depth
(number of unmatched downs) is exactly one.
The previous required use of refresh_mems(), anytime that
the cpuset_sem semaphore was acquired and the code executed
while holding that semaphore might try to allocate memory, is
no longer required. Two refresh_mems() calls were removed
thanks to this. This is a good change, as failing to get
all the necessary refresh_mems() calls placed was a primary
source of bugs in this cpuset code. The only remaining call
to refresh_mems() is made while doing a memory allocation,
if certain task memory placement data needs to be updated
from its cpuset, due to the cpuset having been changed behind
the tasks back.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch (written by me and also containing many suggestions of Arjan van
de Ven) does a major cleanup of the spinlock code. It does the following
things:
- consolidates and enhances the spinlock/rwlock debugging code
- simplifies the asm/spinlock.h files
- encapsulates the raw spinlock type and moves generic spinlock
features (such as ->break_lock) into the generic code.
- cleans up the spinlock code hierarchy to get rid of the spaghetti.
Most notably there's now only a single variant of the debugging code,
located in lib/spinlock_debug.c. (previously we had one SMP debugging
variant per architecture, plus a separate generic one for UP builds)
Also, i've enhanced the rwlock debugging facility, it will now track
write-owners. There is new spinlock-owner/CPU-tracking on SMP builds too.
All locks have lockup detection now, which will work for both soft and hard
spin/rwlock lockups.
The arch-level include files now only contain the minimally necessary
subset of the spinlock code - all the rest that can be generalized now
lives in the generic headers:
include/asm-i386/spinlock_types.h | 16
include/asm-x86_64/spinlock_types.h | 16
I have also split up the various spinlock variants into separate files,
making it easier to see which does what. The new layout is:
SMP | UP
----------------------------|-----------------------------------
asm/spinlock_types_smp.h | linux/spinlock_types_up.h
linux/spinlock_types.h | linux/spinlock_types.h
asm/spinlock_smp.h | linux/spinlock_up.h
linux/spinlock_api_smp.h | linux/spinlock_api_up.h
linux/spinlock.h | linux/spinlock.h
/*
* here's the role of the various spinlock/rwlock related include files:
*
* on SMP builds:
*
* asm/spinlock_types.h: contains the raw_spinlock_t/raw_rwlock_t and the
* initializers
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* asm/spinlock.h: contains the __raw_spin_*()/etc. lowlevel
* implementations, mostly inline assembly code
*
* (also included on UP-debug builds:)
*
* linux/spinlock_api_smp.h:
* contains the prototypes for the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*
* on UP builds:
*
* linux/spinlock_type_up.h:
* contains the generic, simplified UP spinlock type.
* (which is an empty structure on non-debug builds)
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* linux/spinlock_up.h:
* contains the __raw_spin_*()/etc. version of UP
* builds. (which are NOPs on non-debug, non-preempt
* builds)
*
* (included on UP-non-debug builds:)
*
* linux/spinlock_api_up.h:
* builds the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*/
All SMP and UP architectures are converted by this patch.
arm, i386, ia64, ppc, ppc64, s390/s390x, x64 was build-tested via
crosscompilers. m32r, mips, sh, sparc, have not been tested yet, but should
be mostly fine.
From: Grant Grundler <grundler@parisc-linux.org>
Booted and lightly tested on a500-44 (64-bit, SMP kernel, dual CPU).
Builds 32-bit SMP kernel (not booted or tested). I did not try to build
non-SMP kernels. That should be trivial to fix up later if necessary.
I converted bit ops atomic_hash lock to raw_spinlock_t. Doing so avoids
some ugly nesting of linux/*.h and asm/*.h files. Those particular locks
are well tested and contained entirely inside arch specific code. I do NOT
expect any new issues to arise with them.
If someone does ever need to use debug/metrics with them, then they will
need to unravel this hairball between spinlocks, atomic ops, and bit ops
that exist only because parisc has exactly one atomic instruction: LDCW
(load and clear word).
From: "Luck, Tony" <tony.luck@intel.com>
ia64 fix
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjanv@infradead.org>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Patch to eliminate struct files_struct.file_lock spinlock on the reader side
and use rcu refcounting rcuref_xxx api for the f_count refcounter. The
updates to the fdtable are done by allocating a new fdtable structure and
setting files->fdt to point to the new structure. The fdtable structure is
protected by RCU thereby allowing lock-free lookup. For fd arrays/sets that
are vmalloced, we use keventd to free them since RCU callbacks can't sleep. A
global list of fdtable to be freed is not scalable, so we use a per-cpu list.
If keventd is already handling the current cpu's work, we use a timer to defer
queueing of that work.
Since the last publication, this patch has been re-written to avoid using
explicit memory barriers and use rcu_assign_pointer(), rcu_dereference()
premitives instead. This required that the fd information is kept in a
separate structure (fdtable) and updated atomically.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically. Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure. This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct. It also changes all
the users to refer to the file table using files_fdtable() macro. Subsequent
applciation of RCU becomes easier after this.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Adds a set of primitives to do reference counting for objects that are looked
up without locks using RCU.
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch fixes minor problem that the CPUSETS have when files in the
cpuset filesystem are read after lseek()-ed beyond the EOF.
Signed-off-by: KUROSAWA Takahiro <kurosawa@valinux.co.jp>
Acked-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
For architecture like ia64, the switch stack structure is fairly large
(currently 528 bytes). For context switch intensive application, we found
that significant amount of cache misses occurs in switch_to() function.
The following patch adds a hook in the schedule() function to prefetch
switch stack structure as soon as 'next' task is determined. This allows
maximum overlap in prefetch cache lines for that structure.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Race is as follows. Process A forks process B, both being part of the same
session. Then, A calls disassociate_ctty while B forks C:
A B
==== ====
fork()
copy_signal()
dissasociate_ctty() ....
attach_pid(p, PIDTYPE_SID, p->signal->session);
Now, C can have current->signal->tty pointing to a freed tty structure, as
it hasn't yet been added to the session group (to have its controlling tty
cleared on the diassociate_ctty() call).
This has shown up as an oops but could be even more serious. I haven't
tried to create a test case, but a customer has verified that the patch
below resolves the issue, which was occuring quite frequently. I'll try
and post the test case if i can.
The patch simply checks for a NULL tty *after* it has been attached to the
proper session group and clears it as necessary. Alternatively, we could
simply do the tty assignment after the the process is added to the proper
session group.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
An oversight. We don't want to carry the IO scheduler's "we hold exclusive fs
resources" hint over to the child across fork().
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
