Message-ID: <4B13A8C3.3010605@redhat.com>
Date: Mon, 30 Nov 2009 13:13:07 +0200
From: Avi Kivity <avi@redhat.com>
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To: Tejun Heo <tj@kernel.org>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
       Peter Zijlstra <peterz@infradead.org>, Jiri Slaby <jirislaby@gmail.com>,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
       mm-commits@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>,
       kvm@vger.kernel.org, the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH tip/sched/urgent] sched: revert 498657a478c60be092208422fefa9c7b248729c2
References: <200911250111.nAP1BFg5030254@imap1.linux-foundation.org>  <4B0FEA3E.5050108@gmail.com> <1259335036.6483.440.camel@laptop> <alpine.LFD.2.00.0911271730330.24119@localhost.localdomain> <4B1113C0.30505@redhat.com> <4B138950.9040905@kernel.org> <alpine.LFD.2.00.0911301055000.24119@localhost.localdomain> <4B13A24E.1080100@kernel.org> <4B13A654.8030306@kernel.org>
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On 11/30/2009 01:02 PM, Tejun Heo wrote:
> 498657a478c60be092208422fefa9c7b248729c2 incorrectly assumed that
> preempt wasn't disabled around context_switch() and thus was fixing
> imaginary problem.  It also broke kvm because it depended on
> ->sched_in() to be called with irq enabled so that it can do smp calls
> from there.
>
> Revert the incorrect commit and add comment describing different
> contexts under with the two callbacks are invoked.
>
>    *    notifier: struct preempt_notifier for the task being preempted
>    *    next: the task that's kicking us out
> + *
> + * Please note that sched_in and out are called under different
> + * contexts.  sched_in is called with rq lock held and irq disabled
> + * while sched_out is called without rq lock and irq enabled.
>    */
>    

Is this transposed?  sched_in must be called with interrupts enabled for 
the kvm IPI to work.

-- 
error compiling committee.c: too many arguments to function

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