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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: 2ce7135adc ("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>
This commit is contained in:
Olof Johansson 2018-11-16 15:08:00 -08:00 committed by Linus Torvalds
parent ca0246bb97
commit 8fcb2312d1
1 changed files with 24 additions and 23 deletions
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47
kernel/sched/psi.c
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@ -633,38 +633,39 @@ void psi_cgroup_free(struct cgroup *cgroup)
*/ */
void cgroup_move_task(struct task_struct *task, struct css_set *to) void cgroup_move_task(struct task_struct *task, struct css_set *to)
{ {
bool move_psi = !psi_disabled;
unsigned int task_flags = 0; unsigned int task_flags = 0;
struct rq_flags rf; struct rq_flags rf;
struct rq *rq; struct rq *rq;
if (move_psi) { if (psi_disabled) {
rq = task_rq_lock(task, &rf); /*
* Lame to do this here, but the scheduler cannot be locked
if (task_on_rq_queued(task)) * from the outside, so we move cgroups from inside sched/.
task_flags = TSK_RUNNING; */
else if (task->in_iowait) rcu_assign_pointer(task->cgroups, to);
task_flags = TSK_IOWAIT; return;
if (task->flags & PF_MEMSTALL)
task_flags |= TSK_MEMSTALL;
if (task_flags)
psi_task_change(task, task_flags, 0);
} }
/* rq = task_rq_lock(task, &rf);
* Lame to do this here, but the scheduler cannot be locked
* from the outside, so we move cgroups from inside sched/. if (task_on_rq_queued(task))
*/ task_flags = TSK_RUNNING;
else if (task->in_iowait)
task_flags = TSK_IOWAIT;
if (task->flags & PF_MEMSTALL)
task_flags |= TSK_MEMSTALL;
if (task_flags)
psi_task_change(task, task_flags, 0);
/* See comment above */
rcu_assign_pointer(task->cgroups, to); rcu_assign_pointer(task->cgroups, to);
if (move_psi) { if (task_flags)
if (task_flags) psi_task_change(task, 0, task_flags);
psi_task_change(task, 0, task_flags);
task_rq_unlock(rq, task, &rf); task_rq_unlock(rq, task, &rf);
}
} }
#endif /* CONFIG_CGROUPS */ #endif /* CONFIG_CGROUPS */