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    SubjectRe: [tip:perf/urgent] perf_event, x86: Fix 'perf sched record' crashing the machine
    From
    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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