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From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [x86] BUG: unable to handle kernel paging request at 00740060
Date: Tue, 8 Oct 2013 16:34:00 +0200	[thread overview]
Message-ID: <20131008143400.GA14721@redhat.com> (raw)
In-Reply-To: <CA+55aFxEeKixnH7mZZs5iwupA9_GsRN0N7QZxqcTcE4RKZvTTg@mail.gmail.com>

I'll try to find other messages to understand what you are talking
about, just one note for now....

On 10/07, Linus Torvalds wrote:
>
> Your oops makes very little sense, it looks like task_work_run() just
> called out to random crap, probably because the work was already
> released, so "work->func()" ends up being bad.

Or task_work_run() can hit work->func == NULL if do_exit() is called
twice if, say, the task does BUG() after exit_task_work().

> participants anyway, just in case there is some race. The comment says
> that it can race with task_work_cancel() playing with *work. Oleg,
> comments?

The comment tries to say that if we are racing with task_work_cancel()
it can't delete the first entry == work, we won the race, its
cmpxchg(task->task_works) should fail.

Howver, task_work_cancel() can delete one of the next entries and
change, say, work->next. And we need to wait anyway if it scans this
list.

I'll try to recheck, but so far I do not see anything wrong.

Oleg.


  parent reply	other threads:[~2013-10-08 14:41 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-05 23:44 [x86] BUG: unable to handle kernel paging request at 00740060 Fengguang Wu
2013-10-05 23:47 ` [x86] BUG: unable to handle kernel paging request at 08000060 Fengguang Wu
2013-10-06  7:27   ` Mike Galbraith
2013-10-06  7:36     ` Fengguang Wu
2013-10-07  8:49   ` Peter Zijlstra
2013-10-07  9:17     ` Fengguang Wu
2013-10-07  9:36       ` Peter Zijlstra
2013-10-07  9:46         ` Fengguang Wu
2013-10-07  8:55 ` [x86] BUG: unable to handle kernel paging request at 00740060 Peter Zijlstra
2013-10-07  9:08   ` Peter Zijlstra
2013-10-07 11:32     ` Fengguang Wu
2013-10-07  9:27   ` Fengguang Wu
2013-10-07 18:47 ` Linus Torvalds
2013-10-08  7:51   ` Fengguang Wu
2013-10-08 16:21     ` Linus Torvalds
2013-10-08 17:15       ` [x86] BUG: unable to handle kernel NULL pointer dereference at (null) Fengguang Wu
2013-10-08 17:31         ` Linus Torvalds
2013-10-09  1:09           ` Fengguang Wu
2013-10-09  1:33             ` Linus Torvalds
2013-10-08 18:51       ` [x86] BUG: unable to handle kernel paging request at 00740060 Oleg Nesterov
2013-10-08 19:05         ` Jakub Jelinek
2013-10-08 19:20           ` Linus Torvalds
2013-10-08 19:34             ` Linus Torvalds
2013-10-08 19:35           ` Oleg Nesterov
2013-10-08 19:49             ` Linus Torvalds
2013-10-09  1:43           ` Mike Galbraith
2013-10-08 19:05         ` Linus Torvalds
2013-10-08 16:46     ` Oleg Nesterov
2013-10-08 14:34   ` Oleg Nesterov [this message]
2013-10-09  8:04     ` Fengguang Wu
2013-10-09 12:19       ` Fengguang Wu
2013-10-09 12:21         ` Fengguang Wu
2013-10-09 12:27         ` Peter Zijlstra
2013-10-09 12:52           ` Ingo Molnar
2013-10-09 17:18             ` Ingo Molnar
2013-10-10  2:15               ` Mike Galbraith
2013-10-09 12:56           ` Fengguang Wu
2013-10-09 12:43       ` Oleg Nesterov
2013-10-09 14:07         ` Peter Zijlstra
2013-10-09 14:17           ` Oleg Nesterov
2013-10-09 14:32           ` Ingo Molnar
2013-10-09 14:33           ` Peter Zijlstra
2013-10-09 14:46             ` Peter Zijlstra
2013-10-09 18:16               ` Jakub Jelinek
2013-10-09 18:54                 ` Linus Torvalds
2013-10-09 19:02                 ` Peter Zijlstra
2013-10-09 19:08                   ` Jakub Jelinek
2013-10-10  6:22                     ` Ingo Molnar
2013-10-10  6:51                       ` Jakub Jelinek
2013-10-10  8:04                         ` Jakub Jelinek
2013-10-10  8:24                           ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Ingo Molnar
2013-10-10  8:31                             ` Jakub Jelinek
2013-10-10  8:45                               ` Ingo Molnar
2013-10-10  8:55                                 ` [PATCH, -v2] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Ingo Molnar
2013-10-10 11:56                                   ` Peter Zijlstra
2013-10-10 12:32                                     ` Jakub Jelinek
2013-10-10 13:10                                       ` Peter Zijlstra
2013-10-10 15:04                                         ` Ingo Molnar
2013-10-10 14:04                               ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Richard Henderson
2013-10-10 14:27                                 ` Jakub Jelinek
2013-10-10 15:12                                   ` [PATCH, -v3] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Ingo Molnar
2013-10-10 16:15                                     ` Richard Henderson
2013-10-10 16:49                                       ` Ingo Molnar
2013-10-11  4:35                                     ` Fengguang Wu
2013-10-11  5:46                                       ` Ingo Molnar
2013-10-11  6:51                                         ` Fengguang Wu
2013-10-11  9:30                                           ` Fengguang Wu
2013-10-12 17:03                                             ` Ingo Molnar
2013-10-10  8:34                             ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Ingo Molnar

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