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>
next prev parent 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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