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cgroup/cpuset: Wake up cpuset_attach_wq tasks in cpuset_cancel_attach()
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After a successful cpuset_can_attach() call which increments the
attach_in_progress flag, either cpuset_cancel_attach() or cpuset_attach()
will be called later. In cpuset_attach(), tasks in cpuset_attach_wq,
if present, will be woken up at the end. That is not the case in
cpuset_cancel_attach(). So missed wakeup is possible if the attach
operation is somehow cancelled. Fix that by doing the wakeup in
cpuset_cancel_attach() as well.

Fixes: e44193d ("cpuset: let hotplug propagation work wait for task attaching")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Cc: stable@vger.kernel.org # v3.11+
Signed-off-by: Tejun Heo <tj@kernel.org>
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Waiman Long authored and Tejun Heo committed Apr 12, 2023
1 parent 57dcd64 commit ba9182a
Showing 1 changed file with 5 additions and 1 deletion.
6 changes: 5 additions & 1 deletion kernel/cgroup/cpuset.c
Original file line number Diff line number Diff line change
@@ -2502,11 +2502,15 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
static void cpuset_cancel_attach(struct cgroup_taskset *tset)
{
struct cgroup_subsys_state *css;
struct cpuset *cs;

cgroup_taskset_first(tset, &css);
cs = css_cs(css);

percpu_down_write(&cpuset_rwsem);
css_cs(css)->attach_in_progress--;
cs->attach_in_progress--;
if (!cs->attach_in_progress)
wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem);
}

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