Re: perf: stalls in perf_install_in_context/perf_remove_from_context

[Dmitry Vyukov]

On Tue, Dec 15, 2015 at 2:39 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Tue, Dec 15, 2015 at 02:01:32PM +0100, Dmitry Vyukov wrote:
>
>
>> Call Trace:
>>  <IRQ>  [<ffffffff810e5e38>] sched_show_task+0x148/0x250 kernel/sched/core.c:4934
>
>  <snip>
>
>>  [<ffffffff823ff46c>] apic_timer_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:520
>>
>>  <EOI>  [<     inline     >] ? arch_local_irq_enable ./arch/x86/include/asm/paravirt.h:816
>>  <EOI>  [<     inline     >] ? __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:170
>>  <EOI>  [<ffffffff823fde9e>] ? _raw_spin_unlock_irq+0x2e/0x40 kernel/locking/spinlock.c:199
>>  [<     inline     >] ? __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:170
>>  [<ffffffff823fde97>] ? _raw_spin_unlock_irq+0x27/0x40 kernel/locking/spinlock.c:199
>>  [<ffffffff8119c8bb>] perf_install_in_context+0x6b/0xf0 kernel/events/core.c:2173
>>  [<ffffffff811a492c>] SYSC_perf_event_open+0x63c/0xe40 kernel/events/core.c:8565
>>  [<ffffffff811a7739>] SyS_perf_event_open+0x9/0x10 kernel/events/core.c:8261
>>  [<ffffffff823fe676>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185
>
>
> So this looks like its stuck in the retry loop in
> perf_install_in_context(). We do the raw_spin_unlock_irq(), which allows
> the above watchdog interrupt to happen, but make no progress.
>
> This means the task_function_call() thing keeps failing, which is
> extremely unlikely.
>
> Let me have a play with your test-case to see if it reproduces.

Yeah, both perf_install_in_context and perf_remove_from_context hang
in a very similar loops.
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