Cong Wang 3577af70a2 perf: Fix a race condition in perf_remove_from_context() ... We saw a kernel soft lockup in perf_remove_from_context(), it looks like the `perf` process, when exiting, could not go out of the retry loop. Meanwhile, the target process was forking a child. So either the target process should execute the smp function call to deactive the event (if it was running) or it should do a context switch which deactives the event. It seems we optimize out a context switch in perf_event_context_sched_out(), and what's more important, we still test an obsolete task pointer when retrying, so no one actually would deactive that event in this situation. Fix it directly by reloading the task pointer in perf_remove_from_context(). This should cure the above soft lockup. Signed-off-by: Cong Wang <cwang@twopensource.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/1409696840-843-1-git-send-email-xiyou.wangcong@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>		2014-09-09 06:53:42 +02:00
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callchain.c	perf: Roll back callchain buffer refcount under the callchain mutex	2013-08-16 17:55:50 +02:00
core.c	perf: Fix a race condition in perf_remove_from_context()	2014-09-09 06:53:42 +02:00
hw_breakpoint.c	hw_breakpoint: Introduce "struct bp_cpuinfo"	2013-06-20 17:58:57 +02:00
internal.h	perf: Fix arch_perf_out_copy_user default	2013-11-06 12:34:25 +01:00
Makefile	uprobes: Move to kernel/events/	2012-02-22 11:08:00 +01:00
ring_buffer.c	perf: Optimize ring-buffer write by depending on control dependencies	2013-12-11 15:53:22 +01:00
uprobes.c	mm: memcontrol: rewrite charge API	2014-08-08 15:57:17 -07:00