From: Tejun Heo <tj@kernel.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: roland@redhat.com, oleg@redhat.com, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org
Subject: Re: [PATCH 02/14] freezer: fix a race during freezing of TASK_STOPPED tasks
Date: Fri, 26 Nov 2010 20:59:07 +0100 [thread overview]
Message-ID: <4CF0118B.1040708@kernel.org> (raw)
In-Reply-To: <201011262040.27854.rjw@sisk.pl>
On 11/26/2010 08:40 PM, Rafael J. Wysocki wrote:
> On Friday, November 26, 2010, Tejun Heo wrote:
>> After calling freeze_task(), try_to_freeze_tasks() see whether the
>> task is stopped or traced and if so, considers it to be frozen;
>> however, nothing guarantees that either the task being frozen sees
>> TIF_FREEZE or the freezer sees TASK_STOPPED -> TASK_RUNNING
>> transition. The task being frozen may wake up and not see TIF_FREEZE
>> while the freezer fails to notice the transition and believes the task
>> is still stopped.
>>
>> This patch fixes the race by making freeze_task() always go through
>> fake_signal_wake_up() for applicable tasks. The function goes through
>> the target task's scheduler lock and thus guarantees that either the
>> target sees TIF_FREEZE or try_to_freeze_task() sees TASK_RUNNING.
>
> Looks good. I'll take this one to my tree, if you don't mind.
Sure thing.
Thanks.
--
tejun
next prev parent reply other threads:[~2010-11-26 19:59 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-26 10:49 [PATCHSET RFC] ptrace,signal: sane interaction between ptrace and job control signals Tejun Heo
2010-11-26 10:49 ` [PATCH 01/14] signal: fix SIGCONT notification code Tejun Heo
2010-11-26 13:49 ` Oleg Nesterov
2010-12-01 1:43 ` Roland McGrath
2010-11-26 10:49 ` [PATCH 02/14] freezer: fix a race during freezing of TASK_STOPPED tasks Tejun Heo
2010-11-26 19:40 ` Rafael J. Wysocki
2010-11-26 19:59 ` Tejun Heo [this message]
2010-11-26 10:49 ` [PATCH 03/14] freezer: remove superflous try_to_freeze() loop in do_signal_stop() Tejun Heo
2010-11-26 19:42 ` Rafael J. Wysocki
2010-11-26 10:49 ` [PATCH 04/14] signal: don't notify parent if not stopping after tracehook_notify_jctl() " Tejun Heo
2010-11-26 14:46 ` Oleg Nesterov
2010-11-26 15:04 ` Tejun Heo
2010-11-26 10:49 ` [PATCH 05/14] signal: fix premature completion of group stop when interfered by ptrace Tejun Heo
2010-11-26 15:40 ` Oleg Nesterov
2010-11-26 16:03 ` Tejun Heo
2010-11-26 10:49 ` [PATCH 06/14] signal: use GROUP_STOP_PENDING to avoid stopping multiple times for a single group stop Tejun Heo
2010-11-26 17:59 ` Oleg Nesterov
2010-11-26 18:39 ` Tejun Heo
2010-11-27 11:40 ` [PATCH UPDATED " Tejun Heo
2010-11-28 19:07 ` Oleg Nesterov
2010-11-29 13:38 ` Tejun Heo
2010-11-26 10:49 ` [PATCH 07/14] ptrace: add @why to ptrace_stop() Tejun Heo
2010-11-26 10:49 ` [PATCH 08/14] ptrace: make do_signal_stop() use ptrace_stop() if the task is being ptraced Tejun Heo
2010-11-28 19:54 ` Oleg Nesterov
2010-11-28 20:22 ` Jan Kratochvil
2010-11-28 20:53 ` Oleg Nesterov
2010-11-26 10:49 ` [PATCH 09/14] ptrace: clean transitions between TASK_STOPPED and TRACED Tejun Heo
2010-11-28 20:25 ` Oleg Nesterov
2010-11-28 20:51 ` Jan Kratochvil
2010-11-29 13:48 ` Tejun Heo
2010-11-26 10:49 ` [PATCH 10/14] ptrace: don't consume group count from ptrace_stop() Tejun Heo
2010-11-26 10:49 ` [PATCH 11/14] ptrace: make group stop notification reliable against ptrace Tejun Heo
2010-11-28 20:30 ` Oleg Nesterov
2010-11-29 13:52 ` Tejun Heo
2010-11-26 10:49 ` [PATCH 12/14] ptrace: reorganize __ptrace_unlink() and ptrace_untrace() Tejun Heo
2010-11-26 10:49 ` [PATCH 13/14] ptrace: make SIGCONT notification reliable against ptrace Tejun Heo
2010-11-26 10:49 ` [PATCH 14/14] ptrace: remove the extra wake_up_process() from ptrace_detach() Tejun Heo
2010-11-28 20:44 ` Oleg Nesterov
2010-11-29 13:55 ` Tejun Heo
2010-11-26 10:55 ` [PATCHSET RFC] ptrace,signal: sane interaction between ptrace and job control signals Tejun Heo
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