linux-kernel - Re: perf sched record hangs machine

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Message-ID: <aa79d98a0909230044q3548cf0bjda62e05e0400edd6@mail.gmail.com>
Date:	Wed, 23 Sep 2009 11:44:39 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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 9/23/09, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Ingo Molnar <mingo@...e.hu> 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.
>>
>> we shouldnt be trying to program the lapic in that case - all ops
>> should be a NOP, including send-ipi-self. Cyrill?
>
> Cyrill, the right fix would be to define a:
>
> 	struct apic apic_none;
>
> with dummy functions injected. Set struct apic *apic to _that_, instead
> of apic_default.
>
> This means that if we manage to detect a local APIC, we will set it to
> apic_default (or some other driver) - but the bootup default will be 'no
> APIC'.
>

May it wait till evening (i'll back from office and take a look)?

> This is a lot cleaner and a lot less error-prone than the direct
> frobbing of the function pointers.
>
> 	Ingo
>
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