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Date: Tue, 12 Jul 2011 12:44:17 +0300
From: Avi Kivity <avi@redhat.com>
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To: Joerg Roedel <joro@8bytes.org>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>, Will Deacon <will.deacon@arm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
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        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Ingo Molnar <mingo@elte.hu>,
        "acme@ghostprotocols.net" <acme@ghostprotocols.net>,
        Jason Wessel <jason.wessel@windriver.com>
Subject: Re: [PATCH 1/3] perf: add context field to perf_event
References: <20110704143655.GE5551@somewhere> <20110711210753.GA3582@e102144-lin.cambridge.arm.com> <4E1BF5A1.5070301@redhat.com> <1310459898.18678.108.camel@twins> <4E1C0F02.9040906@redhat.com> <1310462046.14978.11.camel@twins> <4E1C10F8.6010300@redhat.com> <1310462335.14978.12.camel@twins> <4E1C1373.5080500@redhat.com> <1310463060.14978.17.camel@twins> <20110712094131.GA29812@8bytes.org>
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On 07/12/2011 12:41 PM, Joerg Roedel wrote:
> >  Using TIF_bits sounds like a much better solution for this, wakeups are
> >  really rather expensive and its best to avoid extra if at all possible.
>
> I would rather vote for Avi's solution too. Such a functionality is very
> helpful for LWP-perf integration as well (because we need a way to call
> do_mmap for a task != current).
>

It's not needed for that.  See use_mm() (caller must be a kernel thread).

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.