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	 <tip-7d42896628202a551ad1107697cd215dc5fca099@git.kernel.org>
Date: Wed, 23 Sep 2009 13:15:03 +0100
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Subject: Re: [tip:perf/urgent] perf_event, x86: Fix 'perf sched record' 
	crashing the machine
From: Chris Malley <mail@chrismalley.co.uk>
To: mail@chrismalley.co.uk, mingo@redhat.com, hpa@zytor.com,
       linux-kernel@vger.kernel.org, fweisbec@gmail.com, peterz@infradead.org,
       tglx@linutronix.de, gorcunov@gmail.com, mingo@elte.hu
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2009/9/23 tip-bot for Peter Zijlstra <peterz@infradead.org>:
> Commit-ID: ?7d42896628202a551ad1107697cd215dc5fca099
> Gitweb: ? ? http://git.kernel.org/tip/7d42896628202a551ad1107697cd215dc5fca099
> Author: ? ? Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Wed, 23 Sep 2009 11:03:37 +0200
> Committer: ?Ingo Molnar <mingo@elte.hu>
> CommitDate: Wed, 23 Sep 2009 11:25:56 +0200
>
> perf_event, x86: Fix 'perf sched record' crashing the machine
>
> Chris Malley reported that 'perf sched record' sometimes
> crashes his box with:
>
> [ ?389.272175] BUG: unable to handle kernel paging request at ffffb300
> [ ?389.272294] IP: [<c011b0bd>] default_send_IPI_self+0x1d/0x50
> [ ?389.272366] *pde = 0073f067 *pte = 00000000
> [ ?389.274708] Call Trace:
> [ ?389.274752] ?[<c010e3b4>] ? ?set_perf_event_pending+0x14/0x20
> [ ?389.274801] ?[<c01b9751>] ? ?perf_output_unlock+0x121/0x1a0
> [ ?389.274848] ?[<c01b981a>] ? perf_output_end+0x4a/0x70
> [ ?389.274893] ?[<c01ba690>] ? ?__perf_event_overflow+0x240/0x2f0
> [ ?389.274942] ?[<c030963e>] ? atomic64_cmpxchg+0x1e/0x30
> [ ?389.274988] ?[<c01ba8f4>] ? ?perf_swevent_ctx_event+0x1b4/0x1c0
> [ ?389.275035] ?[<c01ba773>] ? ?perf_swevent_ctx_event+0x33/0x1c0
> [ ?389.275081] ?[<c01ba9a7>] ? do_perf_sw_event+0xa7/0x160
> [ ?389.275127] ?[<c01baae2>] ? perf_tp_event+0x82/0xa0
> [ ?389.275174] ?[<c012e9c6>] ? ?ftrace_profile_sched_stat_runtime+0xe6/0x120
> [ ?389.275224] ?[<c012e8e0>] ? ?ftrace_profile_sched_stat_runtime+0x0/0x120
> [ ?389.275273] ?[<c013c85a>] ? update_curr+0x18a/0x230
> [ ?389.275318] ?[<c013cdc5>] ? ?put_prev_task_fair+0x155/0x160
> [ ?389.275366] ?[<c01618b5>] ? sched_clock_cpu+0xd5/0x110
> [ ?389.275413] ?[<c04e7525>] ? _spin_lock_irq+0x45/0x50
> [ ?389.275458] ?[<c04e424e>] ? schedule+0x20e/0xb10
>
> The problem is that the box has no lapic enabled:
>
> ?[ ? ?0.042445] Local APIC not detected. Using dummy APIC emulation.
>
> The below seems like the best fix. We disabled all lapic bits, except
> the self-IPI-resend logic.
>
> Reported-by: Chris Malley <mail@chrismalley.co.uk>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> Cc: Cyrill Gorcunov <gorcunov@gmail.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> LKML-Reference: <7863dc4c0909221409v7893bfd3o4b590d5951a233ba@mail.gmail.com>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
>
> ---
> ?arch/x86/kernel/cpu/perf_event.c | ? ?3 +++
> ?1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index a3c7adb..b5801c3 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -1790,6 +1790,9 @@ void smp_perf_pending_interrupt(struct pt_regs *regs)
> ?void set_perf_event_pending(void)
> ?{
> ?#ifdef CONFIG_X86_LOCAL_APIC
> + ? ? ? if (!x86_pmu.apic || !x86_pmu_initialized())
> + ? ? ? ? ? ? ? return;
> +
> ? ? ? ?apic->send_IPI_self(LOCAL_PENDING_VECTOR);
> ?#endif
> ?}
>

Confirmed, this fixes the problem, so FWIW:

Tested-by: Chris Malley <mail@chrismalley.co.uk>
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