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Date: Thu, 11 Nov 2010 21:29:22 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
        Markus Trippelsdorf <markus@trippelsdorf.de>
Subject: Re: [RFC/RFT PATCH v3] sched: automated per tty task groups
Message-ID: <20101111202922.GB16282@redhat.com>
References: <20101021105114.GA10216@Krystal> <1287660312.3488.103.camel@twins> <20101021162924.GA3225@redhat.com> <1288076838.11930.1.camel@marge.simson.net> <1288078144.7478.9.camel@marge.simson.net> <AANLkTimOJAv2uRfq4bW_QPngkGCmJDjNX5n_izpX=eB8@mail.gmail.com> <1289489200.11397.21.camel@maggy.simson.net> <AANLkTinbtfuipoene_M0Om_QtycHGL15Q5E8BOmLU-bh@mail.gmail.com> <1289502511.11397.36.camel@maggy.simson.net> <AANLkTi=hKhsU0Nsenq-jezDVNYQ4fCXFBbUy5c7EFk=U@mail.gmail.com>
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On 11/11, Linus Torvalds wrote:
>
> Well, it cuts both ways. Maybe your approach is simpler and avoids
> overhead at scheduling time. And "tsk->signal" may not be reliable due
> to races with exit etc, so it may well be that going through the
> signal struct could end up being a source of nasty races. I didn't
> look whether the scheduler already derefenced ->signal for some other
> reason, for example.

Just in case, starting from 2.6.35 tsk->signal is reliable.

Oleg.