Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-17 08:31:39 +00:00
Code Issues Packages Projects Releases Wiki Activity
440253c17f
linux/kernel
History
Lai Jiangshan 440253c17f rcu: Increment upper bit only for srcu_read_lock() 
The purpose of the upper bit of SRCU's per-CPU counters is to guarantee
that no reasonable series of srcu_read_lock() and srcu_read_unlock()
operations can return the value of the counter to its original value.
This guarantee is require only after the index has been switched to
the other set of counters, so at most one srcu_read_lock() can affect
a given CPU's counter.  The number of srcu_read_unlock() operations
on a given counter is limited to the number of tasks in the system,
which given the Linux kernel's current structure is limited to far less
than 2^30 on 32-bit systems and far less than 2^62 on 64-bit systems.
(Something about a limited number of bytes in the kernel's address space.)

Therefore, if srcu_read_lock() increments the upper bits, then
srcu_read_unlock() need not do so.  In this case, an srcu_read_lock() and
an srcu_read_unlock() will flip the lower bit of the upper field of the
counter.  An unreasonably large additional number of srcu_read_unlock()
operations would be required to return the counter to its initial value,
thus preserving the guarantee.

This commit takes this approach, which further allows it to shrink
the size of the upper field to one bit, making the number of
srcu_read_unlock() operations required to return the counter to its
initial value even more unreasonable than before.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-04-30 10:48:20 -07:00
..
debug KGDB/KDB regression fixes 2012-04-04 17:26:08 -07:00
events Merge branch 'linus' into perf/urgent 2012-03-26 17:19:03 +02:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq irq_domain: fix type mismatch in debugfs output format 2012-04-12 16:25:48 -06:00
power PM / QoS: add pm_qos_update_request_timeout() API 2012-03-28 23:31:24 +02:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-31 13:35:31 -07:00
time clockevents: tTack broadcast device mode change in tick_broadcast_switch_to_oneshot() 2012-04-10 11:42:07 +02:00
trace Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
.gitignore
acct.c Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-01-08 12:19:57 -08:00
async.c kernel/async: remove redundant declaration. 2012-01-13 09:32:18 +10:30
audit_tree.c audit_tree,rcu: Convert call_rcu(__put_tree) to kfree_rcu() 2011-07-20 14:10:11 -07:00
audit_watch.c
audit.c constify path argument of audit_log_d_path() 2012-03-20 21:29:40 -04:00
audit.h audit: remove AUDIT_SETUP_CONTEXT as it isn't used 2012-01-17 16:16:57 -05:00
auditfilter.c audit: allow interfield comparison in audit rules 2012-01-17 16:17:01 -05:00
auditsc.c kernel-doc: fix new warnings in auditsc.c 2012-01-23 08:44:53 -08:00
backtracetest.c
bounds.c
capability.c Revert "capabitlies: ns_capable can use the cap helpers rather than lsm call" 2012-01-17 10:19:41 -08:00
cgroup_freezer.c cgroup: remove cgroup_subsys argument from callbacks 2012-02-02 09:20:22 -08:00
cgroup.c cgroup: cgroup_attach_task() could return -errno after success 2012-03-29 22:03:33 -07:00
compat.c compat: Add helper functions to read/write struct timeval, timespec 2012-02-20 12:48:47 -08:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu_pm.c cpu_pm: call notifiers during suspend 2011-09-23 12:05:29 +05:30
cpu.c Merge branch 'pm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm 2012-01-08 13:10:57 -08:00
cpuset.c Autogenerated GPG tag for Rusty D1ADB8F1: 15EE 8D6C AB0E 7F0C F999 BFCB D920 0E6C D1AD B8F1 2012-04-02 08:53:24 -07:00
crash_dump.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cred.c cred: copy_process() should clear child->replacement_session_keyring 2012-04-11 08:20:11 -07:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
elfcore.c
exec_domain.c
exit.c Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
extable.c extable, core_kernel_data(): Make sure all archs define _sdata 2011-05-20 08:56:56 +02:00
fork.c prctl: add PR_{SET,GET}_CHILD_SUBREAPER to allow simple process supervision 2012-03-23 16:58:32 -07:00
freezer.c PM / Freezer: Remove references to TIF_FREEZE in comments 2012-03-04 23:08:54 +01:00
futex_compat.c futex: Mark get_robust_list as deprecated 2012-03-29 11:37:17 +02:00
futex.c futex: Mark get_robust_list as deprecated 2012-03-29 11:37:17 +02:00
groups.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
hrtimer.c Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2011-11-28 08:43:52 -08:00
hung_task.c hung_task: fix the broken rcu_lock_break() logic 2012-03-05 15:49:42 -08:00
irq_work.c irq_work: fix compile failure on tile from missing include 2012-04-13 13:15:16 -04:00
itimer.c itimer: Use printk_once instead of WARN_ONCE 2012-04-10 11:00:30 +02:00
jump_label.c static keys: Inline the static_key_enabled() function 2012-02-28 20:01:08 +01:00
kallsyms.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
Kconfig.preempt locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
kexec.c Merge branch 'akpm' (Andrew's patch-bomb) 2012-03-28 17:19:28 -07:00
kfifo.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
kmod.c PM / Sleep: Mitigate race between the freezer and request_firmware() 2012-03-28 23:30:28 +02:00
kprobes.c kprobes: return proper error code from register_kprobe() 2012-03-05 15:49:42 -08:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c freezer: kill unused set_freezable_with_signal() 2011-11-23 09:28:17 -08:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_internals.h
lockdep_proc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_states.h
lockdep.c lockdep: Add CPU-idle/offline warning to lockdep-RCU splat 2012-02-21 09:06:06 -08:00
Makefile sysctl: Move the implementation into fs/proc/proc_sysctl.c 2012-01-24 16:37:54 -08:00
module.c module: Remove module size limit 2012-03-26 12:50:53 +10:30
mutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex-debug.h
mutex.c sched/rt: Use schedule_preempt_disabled() 2012-03-01 10:28:03 +01:00
mutex.h
notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nsproxy.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
padata.c padata: Fix cpu hotplug 2012-03-29 19:52:46 +08:00
panic.c panic: fix stack dump print on direct call to panic() 2012-04-12 13:12:12 -07:00
params.c params: <level>_initcall-like kernel parameters 2012-03-26 12:50:51 +10:30
pid_namespace.c pidns: add reboot_pid_ns() to handle the reboot syscall 2012-03-28 17:14:36 -07:00
pid.c vfs: fix panic in __d_lookup() with high dentry hashtable counts 2012-02-13 20:45:38 -05:00
posix-cpu-timers.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
posix-timers.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
printk.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-20 10:31:44 -07:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c ptrace: remove PTRACE_SEIZE_DEVEL bit 2012-03-23 16:58:41 -07:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Allow nesting of rcu_idle_enter() and rcu_idle_exit() 2012-02-21 09:06:12 -08:00
rcupdate.c rcu: Check for illegal use of RCU from offlined CPUs 2012-02-21 09:06:03 -08:00
rcutiny_plugin.h rcu: Simplify unboosting checks 2012-02-21 09:03:43 -08:00
rcutiny.c rcu: Add RCU_NONIDLE() for idle-loop RCU read-side critical sections 2012-02-21 09:06:13 -08:00
rcutorture.c rcu: Direct algorithmic SRCU implementation 2012-04-30 10:48:19 -07:00
rcutree_plugin.h rcu: Hold off RCU_FAST_NO_HZ after timer posted 2012-02-21 09:42:30 -08:00
rcutree_trace.c rcu: Rework detection of use of RCU by offline CPUs 2012-02-21 09:06:07 -08:00
rcutree.c rcu: Stop spurious warnings from synchronize_sched_expedited 2012-02-21 15:33:34 -08:00
rcutree.h rcu: Rework detection of use of RCU by offline CPUs 2012-02-21 09:06:07 -08:00
relay.c relay: prevent integer overflow in relay_open() 2012-02-10 09:04:49 +01:00
res_counter.c net: introduce res_counter_charge_nofail() for socket allocations 2012-01-22 15:08:46 -05:00
resource.c kernel/resource.c: move EXPORT_SYMBOL right after definition 2012-02-03 23:37:07 +01:00
rtmutex_common.h
rtmutex-debug.c lockdep, rtmutex, bug: Show taint flags on error 2011-12-06 08:16:49 +01:00
rtmutex-debug.h
rtmutex-tester.c rtmutex-tester: convert sysdev_class to a regular subsystem 2011-12-14 14:54:22 -08:00
rtmutex.c Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" 2011-12-11 10:33:18 -08:00
rtmutex.h
rwsem.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
seccomp.c seccomp: audit abnormal end to a process due to seccomp 2012-01-17 16:16:55 -05:00
semaphore.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
signal.c Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
smp.c smp: add func to IPI cpus based on parameter func 2012-03-28 17:14:35 -07:00
softirq.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-20 10:32:09 -07:00
spinlock.c locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
srcu.c rcu: Increment upper bit only for srcu_read_lock() 2012-04-30 10:48:20 -07:00
stacktrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stop_machine.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sys_ni.c Cross Memory Attach 2011-10-31 17:30:44 -07:00
sys.c pidns: add reboot_pid_ns() to handle the reboot syscall 2012-03-28 17:14:36 -07:00
sysctl_binary.c binary_sysctl(): fix memory leak 2011-12-20 10:25:04 -08:00
sysctl.c sysctl: fix write access to dmesg_restrict/kptr_restrict 2012-04-05 14:51:43 +10:00
taskstats.c Make TASKSTATS require root access 2011-09-19 17:04:37 -07:00
test_kprobes.c
time.c time: Remove bogus comments 2012-03-15 18:17:55 -07:00
timeconst.pl
timer.c Merge branch 'core-debugobjects-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 07:53:34 -08:00
tracepoint.c static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() 2012-02-24 10:05:59 +01:00
tsacct.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
uid16.c
up.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user_namespace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user-return-notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
utsname_sysctl.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
utsname.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
wait.c lockdep/waitqueues: Add better annotation 2011-12-21 10:07:39 +01:00
watchdog.c kernel/watchdog.c: add comment to watchdog() exit path 2012-03-23 16:58:32 -07:00
workqueue_sched.h
workqueue.c Merge branch 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2012-03-20 18:13:22 -07:00