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From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Jones <davej@redhat.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	rostedt <rostedt@goodmis.org>, dhowells <dhowells@redhat.com>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: lockdep trace from posix timers
Date: Fri, 17 Aug 2012 17:17:47 +0200	[thread overview]
Message-ID: <20120817151747.GA8248@redhat.com> (raw)
In-Reply-To: <20120817151447.GA7918@redhat.com>

On 08/17, Oleg Nesterov wrote:
>
> On 08/16, Peter Zijlstra wrote:
> >
> >      write_lock_irq(&tasklist_lock)
> >      task_lock(parent)		parent->alloc_lock
>
> And this is already wrong. See the comment above task_lock().
>
> > And since it_lock is IRQ-safe and alloc_lock isn't, you've got the IRQ
> > inversion deadlock reported.
>
> Yes. Or, IOW, write_lock(tasklist) is IRQ-safe and thus it can't nest
> with alloc_lock.
>
> > David, Al, anybody want to have a go at fixing this?
>
> I still think that task_work_add() should synhronize with exit_task_work()
> itself and fail if necessary. But I wasn't able to convince Al ;)

And this is my old patch: http://marc.info/?l=linux-kernel&m=134082268721700
It should be re-diffed of course.

Oleg.


  reply	other threads:[~2012-08-17 15:21 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-24 20:36 lockdep trace from posix timers Dave Jones
2012-07-27 16:20 ` Dave Jones
2012-08-16 12:54   ` Ming Lei
2012-08-16 14:03     ` Dave Jones
2012-08-16 18:07 ` Peter Zijlstra
2012-08-17 15:14   ` Oleg Nesterov
2012-08-17 15:17     ` Oleg Nesterov [this message]
2012-08-17 16:40       ` task_work_add() should not succeed unconditionally (Was: lockdep trace from posix timers) Oleg Nesterov
2012-08-20  7:15     ` lockdep trace from posix timers Peter Zijlstra
2012-08-20 11:44       ` Peter Zijlstra
2012-08-20 11:46         ` Peter Zijlstra
2012-08-20 11:50         ` Peter Zijlstra
2012-08-20 12:19           ` Steven Rostedt
2012-08-20 12:20             ` Peter Zijlstra
2012-08-20 14:59         ` Oleg Nesterov
2012-08-20 15:10           ` Peter Zijlstra
2012-08-20 15:27             ` Peter Zijlstra
2012-08-20 15:32               ` Oleg Nesterov
2012-08-20 15:46                 ` Peter Zijlstra
2012-08-20 15:58                   ` Oleg Nesterov
2012-08-20 16:03                     ` Peter Zijlstra
2012-08-20 15:05         ` Oleg Nesterov
2012-08-20 15:12           ` Peter Zijlstra
2012-08-20 15:41             ` Oleg Nesterov
2012-08-20 15:56               ` Peter Zijlstra
2012-08-20 16:10                 ` Oleg Nesterov
2012-08-20 16:19                   ` Peter Zijlstra
2012-08-20 16:23                     ` Oleg Nesterov
2012-08-21 18:27                       ` Oleg Nesterov
2012-08-21 18:34                         ` Oleg Nesterov
2012-08-24 18:56                           ` Oleg Nesterov
2012-08-26 19:11                             ` [PATCH 0/4] (Was: lockdep trace from posix timers) Oleg Nesterov
2012-08-26 19:12                               ` [PATCH 1/4] task_work: make task_work_add() lockless Oleg Nesterov
2012-09-14  6:08                                 ` [tip:core/urgent] task_work: Make " tip-bot for Oleg Nesterov
2012-09-24 19:27                                 ` [PATCH 1/4] task_work: make " Geert Uytterhoeven
2012-09-24 20:37                                   ` Oleg Nesterov
2012-08-26 19:12                               ` [PATCH 2/4] task_work: task_work_add() should not succeed after exit_task_work() Oleg Nesterov
2012-09-14  6:09                                 ` [tip:core/urgent] " tip-bot for Oleg Nesterov
2012-08-26 19:12                               ` [PATCH 3/4] task_work: revert d35abdb2 "hold task_lock around checks in keyctl" Oleg Nesterov
2012-09-14  6:10                                 ` [tip:core/urgent] task_work: Revert " hold " tip-bot for Oleg Nesterov
2012-08-26 19:12                               ` [PATCH 4/4] task_work: simplify the usage in ptrace_notify() and get_signal_to_deliver() Oleg Nesterov
2012-09-14  6:11                                 ` [tip:core/urgent] task_work: Simplify " tip-bot for Oleg Nesterov
2012-09-06 18:01                               ` [PATCH 0/4] (Was: lockdep trace from posix timers) Oleg Nesterov
2012-09-06 18:35                                 ` Peter Zijlstra
2012-09-07 13:13                                   ` Oleg Nesterov
2012-08-28 16:29                             ` lockdep trace from posix timers Peter Zijlstra
2012-08-28 17:01                               ` Oleg Nesterov
2012-08-28 17:12                                 ` Oleg Nesterov
2012-08-28 17:28                                 ` Peter Zijlstra
2012-08-29 15:25                                   ` Oleg Nesterov
2012-08-20 14:55       ` Oleg Nesterov
2012-08-20 15:43       ` Oleg Nesterov
2012-08-20 15:48         ` Peter Zijlstra
2012-08-20 15:58           ` Oleg Nesterov

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