From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id A30D86B002D for ; Wed, 16 Nov 2011 11:26:31 -0500 (EST) Received: by yenm10 with SMTP id m10so6908607yen.14 for ; Wed, 16 Nov 2011 08:26:30 -0800 (PST) Date: Wed, 16 Nov 2011 08:26:24 -0800 From: Tejun Heo Subject: Re: [PATCH v2] PM/Memory-hotplug: Avoid task freezing failures Message-ID: <20111116162601.GB18919@google.com> References: <20111116115515.25945.35368.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111116115515.25945.35368.stgit@srivatsabhat.in.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Srivatsa S. Bhat" Cc: rjw@sisk.pl, pavel@ucw.cz, lenb@kernel.org, ak@linux.intel.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-mm@kvack.org Hello, On Wed, Nov 16, 2011 at 05:25:23PM +0530, Srivatsa S. Bhat wrote: > v2: Tejun pointed problems with using mutex_lock_interruptible() in a > while loop, when signals not related to freezing are involved. > So, replaced it with mutex_trylock(). > > Signed-off-by: Srivatsa S. Bhat > --- > > include/linux/suspend.h | 14 +++++++++++++- > 1 files changed, 13 insertions(+), 1 deletions(-) > > diff --git a/include/linux/suspend.h b/include/linux/suspend.h > index 57a6924..c2b5aab 100644 > --- a/include/linux/suspend.h > +++ b/include/linux/suspend.h > @@ -5,6 +5,7 @@ > #include > #include > #include > +#include > #include > #include > > @@ -380,7 +381,18 @@ static inline void unlock_system_sleep(void) {} > > static inline void lock_system_sleep(void) > { > - mutex_lock(&pm_mutex); > + /* > + * We should not use mutex_lock() here because, in case we fail to > + * acquire the lock, it would put us to sleep in TASK_UNINTERRUPTIBLE > + * state, which would lead to task freezing failures. As a > + * consequence, hibernation would fail (even though it had acquired > + * the 'pm_mutex' lock). > + * > + * We should use try_to_freeze() in the while loop so that we don't > + * cause freezing failures due to busy looping. > + */ > + while (!mutex_trylock(&pm_mutex)) > + try_to_freeze(); I'm kinda lost. We now always busy-loop if the lock is held by someone else. I can't see how that is an improvement. If this isn't an immediate issue, wouldn't it be better to wait for proper solution? Thank you. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org