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Shailabh Nagar bb129994c3 [PATCH] Remove down_write() from taskstats code invoked on the exit() path 
In send_cpu_listeners(), which is called on the exit path, a down_write()
was protecting operations like skb_clone() and genlmsg_unicast() that do
GFP_KERNEL allocations.  If the oom-killer decides to kill tasks to satisfy
the allocations,the exit of those tasks could block on the same semphore.

The down_write() was only needed to allow removal of invalid listeners from
the listener list.  The patch converts the down_write to a down_read and
defers the removal to a separate critical region.  This ensures that even
if the oom-killer is called, no other task's exit is blocked as it can
still acquire another down_read.

Thanks to Andrew Morton & Herbert Xu for pointing out the oom related
pitfalls, and to Chandra Seetharaman for suggesting this fix instead of
using something more complex like RCU.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-14 21:53:57 -07:00
..
irq Merge git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc 2006-07-03 15:28:34 -07:00
power [PATCH] remove kernel/power/pm.c:pm_unregister_all() 2006-07-12 16:09:08 -07:00
time
.gitignore
acct.c [PATCH] Fix sighand->siglock usage in kernel/acct.c 2006-07-14 21:53:54 -07:00
audit.c
audit.h
auditfilter.c
auditsc.c
capability.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
compat.c
configs.c
cpu.c
cpuset.c
delayacct.c [PATCH] per-task-delay-accounting: /proc export of aggregated block I/O delays 2006-07-14 21:53:57 -07:00
dma.c
exec_domain.c
exit.c [PATCH] per-task delay accounting taskstats interface: control exit data through cpumasks 2006-07-14 21:53:57 -07:00
extable.c
fork.c [PATCH] delay accounting taskstats interface send tgid once 2006-07-14 21:53:57 -07:00
futex_compat.c
futex.c [PATCH] pi-futex: Validate futex type instead of oopsing 2006-07-10 13:24:18 -07:00
hrtimer.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
itimer.c
kallsyms.c [PATCH] null-terminate over-long /proc/kallsyms symbols 2006-07-14 21:53:52 -07:00
Kconfig.hz
Kconfig.preempt
kexec.c
kfifo.c
kmod.c [PATCH] lockdep: annotate on-stack completions 2006-07-03 15:27:09 -07:00
kprobes.c
ksysfs.c
kthread.c [PATCH] remove kernel/kthread.c:kthread_stop_sem() 2006-07-14 21:53:52 -07:00
lockdep_internals.h [PATCH] lockdep: core 2006-07-03 15:27:03 -07:00
lockdep_proc.c [PATCH] lockdep: procfs 2006-07-03 15:27:04 -07:00
lockdep.c [PATCH] lockdep: core, reduce per-lock class-cache size 2006-07-10 13:24:14 -07:00
Makefile [PATCH] per-task-delay-accounting: taskstats interface 2006-07-14 21:53:56 -07:00
module.c [PATCH] null-terminate over-long /proc/kallsyms symbols 2006-07-14 21:53:52 -07:00
mutex-debug.c [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
mutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
mutex.c [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
mutex.h [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
panic.c [PATCH] lockdep: disable lock debugging when kernel state becomes untrusted 2006-07-10 13:24:27 -07:00
params.c
pid.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
posix-cpu-timers.c
posix-timers.c
printk.c [PATCH] kernel/printk.c: EXPORT_SYMBOL_UNUSED 2006-07-10 13:24:17 -07:00
profile.c
ptrace.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
rcupdate.c [PATCH] lockdep: locking init debugging improvement 2006-07-03 15:27:02 -07:00
rcutorture.c
relay.c
resource.c [PATCH] The scheduled unexport of insert_resource 2006-07-12 16:09:08 -07:00
rtmutex_common.h
rtmutex-debug.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
rtmutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex-tester.c [PATCH] Add try_to_freeze() to rt-test kthreads 2006-07-14 21:53:53 -07:00
rtmutex.c [PATCH] sched: cleanup, remove task_t, convert to struct task_struct 2006-07-03 15:27:11 -07:00
rtmutex.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rwsem.c [PATCH] lockdep: prove rwsem locking correctness 2006-07-03 15:27:04 -07:00
sched.c [PATCH] per-task-delay-accounting: cpu delay collection via schedstats 2006-07-14 21:53:56 -07:00
seccomp.c
signal.c
softirq.c [PATCH] unexport open_softirq 2006-07-14 21:53:53 -07:00
softlockup.c
spinlock.c [PATCH] lockdep: prove spinlock rwlock locking correctness 2006-07-03 15:27:04 -07:00
stacktrace.c [PATCH] lockdep: stacktrace subsystem, core 2006-07-03 15:27:02 -07:00
stop_machine.c [PATCH] revert "kthread: convert stop_machine into a kthread" 2006-07-03 21:25:20 -07:00
sys_ni.c
sys.c [PATCH] Fix prctl privilege escalation and suid_dumpable (CVE-2006-2451) 2006-07-12 12:50:25 -07:00
sysctl.c [PATCH] ZVC/zone_reclaim: Leave 1% of unmapped pagecache pages for file I/O 2006-07-03 15:26:59 -07:00
taskstats.c [PATCH] Remove down_write() from taskstats code invoked on the exit() path 2006-07-14 21:53:57 -07:00
time.c
timer.c [PATCH] improve timekeeping resume robustness 2006-07-14 21:53:54 -07:00
uid16.c
unwind.c
user.c
wait.c [PATCH] uninline init_waitqueue_head() 2006-07-10 13:24:25 -07:00
workqueue.c Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq 2006-07-04 14:00:26 -07:00