linux-kernel - Re: perf sched record hangs machine

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Date:	Wed, 23 Sep 2009 11:03:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Chris Malley <mail@...ismalley.co.uk>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: perf sched record hangs machine

On Wed, 2009-09-23 at 09:32 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> >         .size   default_send_IPI_self, .-default_send_IPI_self
> > 
> > Which seems to suggest that cmove is in __prepare_ICR, but I'm not 
> > sure how that can cause a page-fault, as that function is rather 
> > pointer-less.
> > 
> > Did it maybe delay evaluating apic->dest_logical that late, it appear 
> > to be the first usage of that argument?
> > 
> > Ingo, any ideas?
> 
> Yeah, the problem is:
> 
> [    0.042445] Local APIC not detected. Using dummy APIC emulation.

The below seems like the best fix. You disabled all lapic bits, except
that one.

---
 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
 }

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