From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [GIT PULL pm-next] freezer: fix various bugs and simplify implementation Date: Mon, 22 Aug 2011 20:50:59 +0200 Message-ID: <201108222050.59374.rjw__29143.7829997905$1314039107$gmane$org@sisk.pl> References: <20110820094434.GA24151@htj.dyndns.org> <201108212003.14722.rjw@sisk.pl> <20110822095857.GD24151@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110822095857.GD24151@htj.dyndns.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Tejun Heo Cc: arnd@arndb.de, paul@paulmenage.org, lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org, oleg@redhat.com, Martin Schwidefsky , linux-pm@lists.linux-foundation.org List-Id: linux-pm@vger.kernel.org On Monday, August 22, 2011, Tejun Heo wrote: > Hello, Rafael. > > On Sun, Aug 21, 2011 at 08:03:14PM +0200, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki > > Subject: PM / Freezer: Move might_sleep() from try_to_freeze() > > > > There are some code paths that call try_to_freeze() from interrupt > > context, but doing so they know that the current process cannot > > possible be freezing (e.g. during reboot on ARM). However, the > > recently added might_sleep() annotation in try_to_freeze() > > triggers in those cases, making it look like there were bugs in > > those places, which really isn't the case. > > > > Therefore move might_sleep() from try_to_freeze() to > > __refrigerator() so that it doesn't produce false positives. > > Hmmm... I can't quite agree with this change. Some invocations of > try_to_freeze() can be very difficult to trigger. Freezing isn't a > frequent operation after some try_to_freeze() can be buried in weird > places. might_sleep() is exactly to detect context bugs in these > situations. If a code path is called from both sleepable and > unsleepable context and it knows that the latter wouldn't happen if > the system is freezing, that code path should conditionalize > invocation of try_to_freeze() based on its knowledge of context. That > way, all other normal cases get the might_sleep() protection and the > peculiar logic in that code path is explicitly described - win win. > > Can you please point me to where the problem was? Apparently, during reboot on ARM try_to_freeze() is called via do_signal() with interrupts disabled. Thanks, Rafael