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7fe70b579c
linux/kernel
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Steven Rostedt (Red Hat) 7fe70b579c tracing: Fix ftrace_dump() 
ftrace_dump() had a lot of issues. What ftrace_dump() does, is when
ftrace_dump_on_oops is set (via a kernel parameter or sysctl), it
will dump out the ftrace buffers to the console when either a oops,
panic, or a sysrq-z occurs.

This was written a long time ago when ftrace was fragile to recursion.
But it wasn't written well even for that.

There's a possible deadlock that can occur if a ftrace_dump() is happening
and an NMI triggers another dump. This is because it grabs a lock
before checking if the dump ran.

It also totally disables ftrace, and tracing for no good reasons.

As the ring_buffer now checks if it is read via a oops or NMI, where
there's a chance that the buffer gets corrupted, it will disable
itself. No need to have ftrace_dump() do the same.

ftrace_dump() is now cleaned up where it uses an atomic counter to
make sure only one dump happens at a time. A simple atomic_inc_return()
is enough that is needed for both other CPUs and NMIs. No need for
a spinlock, as if one CPU is running the dump, no other CPU needs
to do it too.

The tracing_on variable is turned off and not turned on. The original
code did this, but it wasn't pretty. By just disabling this variable
we get the result of not seeing traces that happen between crashes.

For sysrq-z, it doesn't get turned on, but the user can always write
a '1' to the tracing_on file. If they are using sysrq-z, then they should
know about tracing_on.

The new code is much easier to read and less error prone. No more
deadlock possibility when an NMI triggers here.

Reported-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: stable@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2013-03-15 19:24:56 -04:00
..
debug module: add new state MODULE_STATE_UNFORMED. 2013-01-12 13:27:05 +10:30
events Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 17:49:41 -08:00
gcov
irq Merge branch 'x86-apic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 19:07:27 -08:00
power Merge branch 'for-3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-12-12 08:18:24 -08:00
sched Merge branch 'for-3.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2013-02-19 22:01:33 -08:00
time Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 19:05:45 -08:00
trace tracing: Fix ftrace_dump() 2013-03-15 19:24:56 -04:00
.gitignore
acct.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
async.c Merge branch 'for-3.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2013-02-19 22:01:33 -08:00
audit_tree.c audit: catch possible NULL audit buffers 2013-01-11 14:54:55 -08:00
audit_watch.c audit: catch possible NULL audit buffers 2013-01-11 14:54:55 -08:00
audit.c kernel/audit.c: avoid negative sleep durations 2013-01-11 14:54:56 -08:00
audit.h audit: optimize audit_compare_dname_path 2012-10-12 00:32:02 -04:00
auditfilter.c audit: fix auditfilter.c kernel-doc warnings 2013-01-10 14:35:23 -08:00
auditsc.c audit: catch possible NULL audit buffers 2013-01-11 14:54:55 -08:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free() 2012-11-19 08:13:38 -08:00
cgroup.c Merge branch 'akpm' (Andrew's patch-bomb) 2012-12-17 20:58:12 -08:00
compat.c x32: fix sigtimedwait 2012-12-26 01:15:03 -05:00
configs.c
context_tracking.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 18:19:48 -08:00
cpu_pm.c kernel/cpu_pm.c: fix various typos 2012-05-31 17:49:27 -07:00
cpu.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 19:04:55 -08:00
cpuset.c cpuset: use N_MEMORY instead N_HIGH_MEMORY 2012-12-12 17:38:32 -08:00
crash_dump.c
cred.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2012-12-18 10:55:28 -08:00
delayacct.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
extable.c
fork.c This implements the cputime accounting on full dynticks CPUs. 2013-02-05 13:10:33 +01:00
freezer.c freezer: change ptrace_stop/do_signal_stop to use freezable_schedule() 2012-10-26 14:27:49 -07:00
futex_compat.c
futex.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
groups.c
hrtimer.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 19:05:45 -08:00
hung_task.c
irq_work.c Merge branch 'nohz/printk-v8' into irq/core 2013-02-05 00:48:46 +01:00
itimer.c
jump_label.c jump_label: Export jump_label_rate_limit() 2012-08-06 19:00:35 +03:00
kallsyms.c
kcmp.c kcmp: include linux/ptrace.h 2012-12-20 17:40:19 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking: Adjust spin lock inlining Kconfig options 2012-09-13 17:56:13 +02:00
Kconfig.preempt
kexec.c kdump: remove unneeded include 2012-10-06 03:05:19 +09:00
kfifo.c
kmod.c Merge branch 'master' into for-3.9-async 2013-01-23 09:31:01 -08:00
kprobes.c Merge branch 'for-3.9-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2013-02-19 21:58:52 -08:00
ksysfs.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-12-11 18:10:49 -08:00
kthread.c kthread: use N_MEMORY instead N_HIGH_MEMORY 2012-12-12 17:38:33 -08:00
latencytop.c
lglock.c
lockdep_internals.h
lockdep_proc.c lockdep: Use KSYM_NAME_LEN'ed buffer for __get_key_name() 2012-10-24 12:39:09 +02:00
lockdep_states.h
lockdep.c lockdep: Check if nested lock is actually held 2012-09-13 17:00:44 +02:00
Makefile Nothing all that exciting; a new module-from-fd syscall for those who want 2012-12-19 07:55:08 -08:00
modsign_certificate.S MODSIGN: Avoid using .incbin in C source 2012-12-14 13:06:44 +10:30
modsign_pubkey.c keys: use keyring_alloc() to create module signing keyring 2012-12-20 17:40:21 -08:00
module_signing.c MODSIGN: Don't use enum-type bitfields in module signature info block 2012-12-05 11:27:24 +10:30
module-internal.h MODSIGN: Move the magic string to the end of a module and eliminate the search 2012-10-19 17:30:40 -07:00
module.c module: fix missing module_mutex unlock 2013-01-20 20:22:58 -08:00
mutex-debug.c
mutex-debug.h
mutex.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
mutex.h
notifier.c
nsproxy.c userns: Implement unshare of the user namespace 2012-11-20 04:18:14 -08:00
padata.c padata: use __this_cpu_read per-cpu helper 2012-12-06 17:16:23 +08:00
panic.c panic: fix a possible deadlock in panic() 2012-07-30 17:25:13 -07:00
params.c
pid_namespace.c pidns: Stop pid allocation when init dies 2012-12-25 16:10:05 -08:00
pid.c kernel/pid.c: reenable interrupts when alloc_pid() fails because init has exited 2013-02-12 14:34:00 -08:00
posix-cpu-timers.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 19:05:45 -08:00
posix-timers.c posix-timers: Fix clock_adjtime to always return timex data on success 2013-01-15 18:16:07 -08:00
printk.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 17:47:58 -08:00
profile.c profiling: Remove unused timer hook 2013-01-24 15:37:26 +01:00
ptrace.c uprobes: Add exports for module use 2013-02-08 17:47:13 +01:00
range.c
rcu.h rcu: Provide RCU CPU stall warnings for tiny RCU 2013-01-28 22:06:21 -08:00
rcupdate.c Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
rcutiny_plugin.h rcu: Provide RCU CPU stall warnings for tiny RCU 2013-01-28 22:06:21 -08:00
rcutiny.c Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
rcutorture.c rcu: Allow rcutorture to be built at low optimization levels 2013-02-04 12:18:20 -08:00
rcutree_plugin.h rcu: Make rcu_nocb_poll an early_param instead of module_param 2013-01-08 14:12:19 -08:00
rcutree_trace.c rcu: Separate accounting of callbacks from callback-free CPUs 2012-11-16 10:05:57 -08:00
rcutree.c Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
rcutree.h Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
relay.c splice: fix racy pipe->buffers uses 2012-06-13 21:16:42 +02:00
res_counter.c res_counter: return amount of charges after res_counter_uncharge() 2012-12-18 15:02:12 -08:00
resource.c kernel/resource.c: fix stack overflow in __reserve_region_with_split() 2012-10-06 03:05:31 +09:00
rtmutex_common.h
rtmutex-debug.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
rtmutex-debug.h
rtmutex-tester.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
rtmutex.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
rtmutex.h
rwsem.c lockdep, rwsem: provide down_write_nest_lock() 2013-01-11 14:54:55 -08:00
seccomp.c seccomp: Make syscall skipping and nr changes more consistent 2012-10-02 21:14:29 +10:00
semaphore.c
signal.c This implements the cputime accounting on full dynticks CPUs. 2013-02-05 13:10:33 +01:00
smp.c smp: Fix SMP function call empty cpu mask race 2013-01-28 11:21:57 +01:00
smpboot.c smpboot: Allow selfparking per cpu threads 2013-02-14 15:29:37 +01:00
smpboot.h smpboot: Provide infrastructure for percpu hotplug threads 2012-08-13 17:01:07 +02:00
softirq.c cputime: Safely read cputime of full dynticks CPUs 2013-01-27 20:35:47 +01:00
spinlock.c
srcu.c srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock() 2013-02-07 15:19:36 -08:00
stacktrace.c
stop_machine.c stop_machine: Use smpboot threads 2013-02-14 15:29:38 +01:00
sys_ni.c module: add syscall to load module from fd 2012-12-14 13:05:22 +10:30
sys.c cputime: Rename thread_group_times to thread_group_cputime_adjusted 2012-11-28 17:07:57 +01:00
sysctl_binary.c pidns: Use task_active_pid_ns where appropriate 2012-11-19 05:59:09 -08:00
sysctl.c sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice 2013-02-07 20:51:07 +01:00
task_work.c task_work: task_work_add() should not succeed after exit_task_work() 2012-09-13 16:47:34 +02:00
taskstats.c taskstats: cgroupstats_user_cmd() may leak on error 2012-10-06 03:05:31 +09:00
test_kprobes.c
time.c time, Fix setting of hardware clock in NTP code 2013-02-08 15:07:05 -08:00
timeconst.pl timeconst.pl: Eliminate Perl warning 2013-02-07 17:14:08 -08:00
timer.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 18:19:48 -08:00
tracepoint.c
tsacct.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
uid16.c
up.c
user_namespace.c userns: Fix typo in description of the limitation of userns_install 2012-12-14 18:36:36 -08:00
user-return-notifier.c
user.c proc: Usable inode numbers for the namespace file descriptors. 2012-11-20 04:19:49 -08:00
utsname_sysctl.c
utsname.c userns: Require CAP_SYS_ADMIN for most uses of setns. 2012-12-14 16:12:03 -08:00
wait.c propagate name change to comments in kernel source 2012-12-06 10:39:54 +01:00
watchdog.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
workqueue_internal.h workqueue: rename cpu_workqueue to pool_workqueue 2013-02-13 19:29:12 -08:00
workqueue.c workqueue: un-GPL function delayed_work_timer_fn() 2013-02-19 10:09:13 -08:00