Re: [PATCH -rt] sched: teach migrate_disable about atomic contexts

From: Arnaldo Carvalho de Melo
Date: Tue Sep 06 2011 - 14:08:31 EST


Em Fri, Sep 02, 2011 at 02:41:37PM +0200, Peter Zijlstra escreveu:
> Subject: sched: teach migrate_disable about atomic contexts
> From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Date: Fri Sep 02 14:29:27 CEST 2011
>
> <NMI> [<ffffffff812dafd8>] spin_bug+0x94/0xa8
> [<ffffffff812db07f>] do_raw_spin_lock+0x43/0xea
> [<ffffffff814fa9be>] _raw_spin_lock_irqsave+0x6b/0x85
> [<ffffffff8106ff9e>] ? migrate_disable+0x75/0x12d
> [<ffffffff81078aaf>] ? pin_current_cpu+0x36/0xb0
> [<ffffffff8106ff9e>] migrate_disable+0x75/0x12d
> [<ffffffff81115b9d>] pagefault_disable+0xe/0x1f
> [<ffffffff81047027>] copy_from_user_nmi+0x74/0xe6
> [<ffffffff810489d7>] perf_callchain_user+0xf3/0x135
>
> Now clearly we can't go around taking locks from NMI context, cure
> this by short-circuiting migrate_disable() when we're in an atomic
> context already.
>
> Add some extra debugging to avoid things like:
>
> preempt_disable()
> migrate_disable();
>
> preempt_enable();
> migrate_enable();
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Link: http://lkml.kernel.org/n/tip-wbot4vsmwhi8vmbf83hsclk6@xxxxxxxxxxxxxx

Now I can collect callchains with perf on linux RT, thanks.

Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

- Arnaldo
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