06f417968b
The '!ctx->is_active' check has a valid scenario, so there's no need for the warning. The reason is that there's a time window between the 'ctx->is_active' check in the perf_event_enable() function and the __perf_event_enable() function having: - IRQs on - ctx->lock unlocked where the task could be killed and 'ctx' deactivated by perf_event_exit_task(), ending up with the warning below. So remove the WARN_ON_ONCE() check and add comments to explain it all. This addresses the following warning reported by Vince Weaver: [ 324.983534] ------------[ cut here ]------------ [ 324.984420] WARNING: at kernel/events/core.c:1953 __perf_event_enable+0x187/0x190() [ 324.984420] Modules linked in: [ 324.984420] CPU: 19 PID: 2715 Comm: nmi_bug_snb Not tainted 3.10.0+ #246 [ 324.984420] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010 [ 324.984420] 0000000000000009 ffff88043fce3ec8 ffffffff8160ea0b ffff88043fce3f00 [ 324.984420] ffffffff81080ff0 ffff8802314fdc00 ffff880231a8f800 ffff88043fcf7860 [ 324.984420] 0000000000000286 ffff880231a8f800 ffff88043fce3f10 ffffffff8108103a [ 324.984420] Call Trace: [ 324.984420] <IRQ> [<ffffffff8160ea0b>] dump_stack+0x19/0x1b [ 324.984420] [<ffffffff81080ff0>] warn_slowpath_common+0x70/0xa0 [ 324.984420] [<ffffffff8108103a>] warn_slowpath_null+0x1a/0x20 [ 324.984420] [<ffffffff81134437>] __perf_event_enable+0x187/0x190 [ 324.984420] [<ffffffff81130030>] remote_function+0x40/0x50 [ 324.984420] [<ffffffff810e51de>] generic_smp_call_function_single_interrupt+0xbe/0x130 [ 324.984420] [<ffffffff81066a47>] smp_call_function_single_interrupt+0x27/0x40 [ 324.984420] [<ffffffff8161fd2f>] call_function_single_interrupt+0x6f/0x80 [ 324.984420] <EOI> [<ffffffff816161a1>] ? _raw_spin_unlock_irqrestore+0x41/0x70 [ 324.984420] [<ffffffff8113799d>] perf_event_exit_task+0x14d/0x210 [ 324.984420] [<ffffffff810acd04>] ? switch_task_namespaces+0x24/0x60 [ 324.984420] [<ffffffff81086946>] do_exit+0x2b6/0xa40 [ 324.984420] [<ffffffff8161615c>] ? _raw_spin_unlock_irq+0x2c/0x30 [ 324.984420] [<ffffffff81087279>] do_group_exit+0x49/0xc0 [ 324.984420] [<ffffffff81096854>] get_signal_to_deliver+0x254/0x620 [ 324.984420] [<ffffffff81043057>] do_signal+0x57/0x5a0 [ 324.984420] [<ffffffff8161a164>] ? __do_page_fault+0x2a4/0x4e0 [ 324.984420] [<ffffffff8161665c>] ? retint_restore_args+0xe/0xe [ 324.984420] [<ffffffff816166cd>] ? retint_signal+0x11/0x84 [ 324.984420] [<ffffffff81043605>] do_notify_resume+0x65/0x80 [ 324.984420] [<ffffffff81616702>] retint_signal+0x46/0x84 [ 324.984420] ---[ end trace 442ec2f04db3771a ]--- Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Jiri Olsa <jolsa@redhat.com> Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1373384651-6109-2-git-send-email-jolsa@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| .. | ||
| callchain.c | ||
| core.c | ||
| hw_breakpoint.c | ||
| internal.h | ||
| Makefile | ||
| ring_buffer.c | ||
| uprobes.c | ||