The patch titled
Subject: kernel/sched/psi.c: simplify cgroup_move_task()
has been added to the -mm tree. Its filename is
psi-simplify-cgroup_move_task.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/psi-simplify-cgroup_move_task.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/psi-simplify-cgroup_move_task.patch
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------------------------------------------------------
From: Olof Johansson <olof@xxxxxxxxx>
Subject: 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@xxxxxxxxx
Fixes: 2ce7135adc9ad ("psi: cgroup support")
Signed-off-by: Olof Johansson <olof@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched/psi.c | 43 ++++++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 21 deletions(-)
--- a/kernel/sched/psi.c~psi-simplify-cgroup_move_task
+++ a/kernel/sched/psi.c
@@ -633,38 +633,39 @@ void psi_cgroup_free(struct cgroup *cgro
*/
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) {
- rq = task_rq_lock(task, &rf);
+ 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;
+ }
- if (task_on_rq_queued(task))
- task_flags = TSK_RUNNING;
- else if (task->in_iowait)
- task_flags = TSK_IOWAIT;
+ rq = task_rq_lock(task, &rf);
- if (task->flags & PF_MEMSTALL)
- task_flags |= TSK_MEMSTALL;
+ if (task_on_rq_queued(task))
+ task_flags = TSK_RUNNING;
+ else if (task->in_iowait)
+ task_flags = TSK_IOWAIT;
- if (task_flags)
- psi_task_change(task, task_flags, 0);
- }
+ if (task->flags & PF_MEMSTALL)
+ task_flags |= TSK_MEMSTALL;
- /*
- * Lame to do this here, but the scheduler cannot be locked
- * from the outside, so we move cgroups from inside sched/.
- */
+ if (task_flags)
+ psi_task_change(task, task_flags, 0);
+
+ /* See comment above */
rcu_assign_pointer(task->cgroups, to);
- if (move_psi) {
- if (task_flags)
- psi_task_change(task, 0, task_flags);
+ if (task_flags)
+ psi_task_change(task, 0, task_flags);
- task_rq_unlock(rq, task, &rf);
- }
+ task_rq_unlock(rq, task, &rf);
}
#endif /* CONFIG_CGROUPS */
_
Patches currently in -mm which might be from olof@xxxxxxxxx are
psi-simplify-cgroup_move_task.patch
