Messages in this thread | | | Date | Thu, 3 Nov 2011 17:17:59 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH pm-for-3.2 2/2] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" |
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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@kernel.org> > > Cc: Jeff Layton <jlayton@redhat.com> > > LKML-Reference: <20111031221743.GA18855@google.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.
Thanks.
-- tejun
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