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Date: Fri, 4 Nov 2011 01:24:33 +0100 From: "Rafael J. Wysocki" <rjw@...k.pl> To: Tejun Heo <tj@...nel.org> Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>, Jeff Layton <jlayton@...hat.com> Subject: Re: [PATCH pm-for-3.2 2/2] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" On Friday, November 04, 2011, Tejun Heo wrote: > Hello, Rafael. > > On Fri, Nov 04, 2011 at 01:13:21AM +0100, Rafael J. Wysocki wrote: > > On Friday, November 04, 2011, Tejun Heo wrote: > > > Commit 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake > > > TASK_KILLABLE tasks too" updated fake_signal_wake_up() used by freezer > > > to wake up KILLABLE tasks. Sending unsolicited wakeups to tasks in > > > killable sleep is dangerous as there are code paths which depend on > > > tasks not waking up spuriously from KILLABLE sleep. > > > > > > For example. sys_read() or page can sleep in TASK_KILLABLE assuming > > > that wait/down/whatever _killable can only fail if we can not return > > > to the usermode. TASK_TRACED is another obvious example. > > > > > > The previous patch updated wait_event_freezekillable() such that it > > > doesn't depend on the spurious wakeup. This patch reverts the > > > offending commit. > > > > > > Note that the spurious KILLABLE wakeup had other implicit effects in > > > KILLABLE sleeps in nfs and cifs and those will need further updates to > > > regain freezekillable behavior. > > > > > > Signed-off-by: Tejun Heo <tj@...nel.org> > > > Cc: Jeff Layton <jlayton@...hat.com> > > > LKML-Reference: <20111031221743.GA18855@...gle.com> > > > > Applied to linux-pm/linux-next. > > Just to be sure, as the commit which changed fake_signal_wake_up() to > use KILLABLE wakeup is already mainline, these two will have to be > pushed as fixes after some time in this devel cycle. Yes, they are 3.2 material and I'm going to push them in the next few days along with a number of other PM-related fixes/cleanups. Is that OK? Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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