From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH -mm 1/2]: PM: Fix handling of stopped tasks Date: Tue, 5 Dec 2006 12:24:29 +0100 Message-ID: <20061205112429.GA7039@elf.ucw.cz> References: <200612032318.29030.rjw@sisk.pl> <200612032350.23067.rjw@sisk.pl> <20061205103429.GB5306@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20061205103429.GB5306@elf.ucw.cz> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: suspend-devel-bounces@lists.sourceforge.net Errors-To: suspend-devel-bounces@lists.sourceforge.net To: "Rafael J. Wysocki" Cc: suspend-devel List , pm list , Stephen Hemminger List-Id: linux-pm@vger.kernel.org Hi! > > Currently, if a task is stopped (ie. it's in the TASK_STOPPED state), it is > > considered by the freezer as unfreezeable. However, there may be a race > > between the freezer and the delivery of the continuation signal to the task > > resulting in the task running after we have finished freezing other tasks. > > This, in turn, may lead to undesirable effects up to and including a > > corruption of data. > > > > To prevent this from happening we first need to make the freezer consider > > stopped tasks as freezeable. For this purpose we need to make freezeable() > > stop returning 0 for these tasks. We must remember, however, that the > > stopped tasks need not receive the continuation signal before thaw_processes() > > is called, so as soon as PF_FREEZE is set for them try_to_freeze_tasks() > > should stop counting them as the ones to wait for. Additionally, if there's a > > traced task (ie. a task in the TASK_TRACED state) the parent of which has > > PF_FREEZE set and is stopped, try_to_freeze_tasks() should not wait for it. > > Moreover, if there are some stopped tasks that haven't received the continuation > > signal before thaw_processes() is called, we must clear PF_FREEZE for them so > > that they don't go to the refrigerator when it's no longer desirable. > > Actually, what do you think about this patch? It removes special > handling of TASK_TRACED, and should do the trick, too... I was surprised, but the patch seems to work okay. Can you replace your 1/2 with this one, and see what breaks? Pavel > diff --git a/kernel/power/process.c b/kernel/power/process.c > index 7bcc976..d56e494 100644 > --- a/kernel/power/process.c > +++ b/kernel/power/process.c > @@ -26,8 +26,7 @@ static inline int freezeable(struct task > (p->flags & PF_NOFREEZE) || > (p->exit_state == EXIT_ZOMBIE) || > (p->exit_state == EXIT_DEAD) || > - ((p->exit_state == TASK_TRACED) && frozen(p->parent)) || > - (p->state == TASK_STOPPED)) > + ((p->exit_state == TASK_TRACED) && frozen(p->parent))) > return 0; > return 1; > } > diff --git a/kernel/signal.c b/kernel/signal.c > index 9a61944..e305ad1 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1702,7 +1702,9 @@ finish_stop(int stop_count) > read_unlock(&tasklist_lock); > } > > - schedule(); > + do { > + schedule(); > + } while (try_to_freeze()); > /* > * Now we don't run again until continued. > */ > > -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV