Commit b822a6da authored Nov 16, 2018 by Olof Johansson Committed by Suren Baghdasaryan Mar 21, 2019

UPSTREAM: kernel/sched/psi.c: simplify cgroup_move_task()

The existing code triggered an invalid warning about 'rq' possibly being
used uninitialized.  Instead of doing the silly warning suppression by
initializa it to NULL, refactor the code to bail out early instead.

Warning was:

  kernel/sched/psi.c: In function `cgroup_move_task':
  kernel/sched/psi.c:639:13: warning: `rq' may be used uninitialized in this function [-Wmaybe-uninitialized]

Link: http://lkml.kernel.org/r/20181103183339.8669-1-olof@lixom.net


Fixes: 2ce7135adc9ad ("psi: cgroup support")
Signed-off-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 8fcb2312d1e3300e81aa871aad00d4c038cfc184)

Bug: 127712811
Test: lmkd in PSI mode
Change-Id: Id989da224a726082e0cfa5d5d9460bf63d448a93
Signed-off-by: Suren Baghdasaryan <surenb@google.com>

parent dc9cd29d

kernel/sched/psi.c

+22 −21

Original line number	Diff line number	Diff line
		@@ -633,12 +633,19 @@ void psi_cgroup_free(struct cgroup *cgroup)
		*/
		void cgroup_move_task(struct task_struct task, struct css_set to)
		{
		bool move_psi = !psi_disabled;
		unsigned int task_flags = 0;
		struct rq_flags rf;
		struct rq *rq;

		if (move_psi) {
		if (psi_disabled) {
		/*
		* Lame to do this here, but the scheduler cannot be locked
		* from the outside, so we move cgroups from inside sched/.
		*/
		rcu_assign_pointer(task->cgroups, to);
		return;
		}

		rq = task_rq_lock(task, &rf);

		if (task_on_rq_queued(task))
		@@ -651,21 +658,15 @@ void cgroup_move_task(struct task_struct task, struct css_set to)

		if (task_flags)
		psi_task_change(task, task_flags, 0);
		}

		/*
		* Lame to do this here, but the scheduler cannot be locked
		* from the outside, so we move cgroups from inside sched/.
		*/
		/* See comment above */
		rcu_assign_pointer(task->cgroups, to);

		if (move_psi) {
		if (task_flags)
		psi_task_change(task, 0, task_flags);

		task_rq_unlock(rq, task, &rf);
		}
		}
		#endif /* CONFIG_CGROUPS */

		int psi_show(struct seq_file m, struct psi_group group, enum psi_res res)