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From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Darren Hart <darren@dvhart.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jerome Marchand <jmarchan@redhat.com>,
	Larry Woodman <lwoodman@redhat.com>,
	Mateusz Guzik <mguzik@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] futex: check PF_KTHREAD rather than !p->mm to filter out kthreads
Date: Wed, 4 Feb 2015 11:48:43 +0100	[thread overview]
Message-ID: <20150204104843.GD2896@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20150202140536.GA26406@redhat.com>

On Mon, Feb 02, 2015 at 03:05:36PM +0100, Oleg Nesterov wrote:
> attach_to_pi_owner() checks p->mm to prevent attaching to kthreads and
> this looks doubly wrong:
> 
> 1. It should actually check PF_KTHREAD, kthread can do use_mm().
> 
> 2. If this task is not kthread and it is actually the lock owner we can
>    wrongly return -EPERM instead of -ESRCH or retry-if-EAGAIN.
> 
>    And note that this wrong EPERM is the likely case unless the exiting
>    task is (auto)reaped quickly, we check ->mm before PF_EXITING.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

  reply	other threads:[~2015-02-04 10:48 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-02 14:05 [PATCH 0/1] futex: check PF_KTHREAD rather than !p->mm to filter out kthreads Oleg Nesterov
2015-02-02 14:05 ` [PATCH 1/1] " Oleg Nesterov
2015-02-04 10:48   ` Peter Zijlstra [this message]
2015-02-14 18:01   ` Davidlohr Bueso
2015-02-14 20:57     ` Oleg Nesterov
2015-02-14 21:15       ` Davidlohr Bueso
2015-02-14 21:54         ` Oleg Nesterov
2015-02-18 17:11   ` [tip:locking/core] locking/futex: Check " tip-bot for Oleg Nesterov
2015-02-02 15:11 ` [PATCH 0/1] futex: check " Peter Zijlstra
2015-02-02 15:13   ` Peter Zijlstra
2015-02-02 15:14     ` Peter Zijlstra
2015-02-02 16:20   ` Oleg Nesterov
2015-02-03 20:09   ` Oleg Nesterov
2015-02-04 11:12     ` Peter Zijlstra
2015-02-04 20:25       ` Oleg Nesterov
2015-02-05 16:27         ` Peter Zijlstra
2015-02-05 18:10           ` Oleg Nesterov
2015-02-06 10:46             ` Peter Zijlstra
2015-02-06 17:04               ` Oleg Nesterov
2015-02-09 20:38                 ` Darren Hart
2015-02-10 11:14                   ` Oleg Nesterov
2015-02-16 20:13 ` [PATCH 0/1] futex: don't spin waiting for PF_EXITING -> PF_EXITPIDONE transition Oleg Nesterov
2015-02-16 20:13   ` [PATCH 1/1] " Oleg Nesterov
2015-02-27  9:52     ` Peter Zijlstra
2015-02-27 11:54       ` Peter Zijlstra

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