sched/core: Streamle calls to task_rq_unlock()

Calls to task_rq_unlock() are done several times in the
__sched_setscheduler() function.  This is fine when only the rq lock needs to be
handled but not so much when other locks come into play.

This patch streamlines the release of the rq lock so that only one
location need to be modified when dealing with more than one lock.

No change of functionality is introduced by this patch.

Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bristot@redhat.com
Cc: claudio@evidence.eu.com
Cc: lizefan@huawei.com
Cc: longman@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: tommaso.cucinotta@santannapisa.it
Link: https://lkml.kernel.org/r/20190719140000.31694-3-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0b22e55..1af3d2d 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4712,8 +4712,8 @@ recheck:
         * Changing the policy of the stop threads its a very bad idea:
         */
        if (p == rq->stop) {
-               task_rq_unlock(rq, p, &rf);
-               return -EINVAL;
+               retval = -EINVAL;
+               goto unlock;
        }
 
        /*
@@ -4731,8 +4731,8 @@ recheck:
                        goto change;
 
                p->sched_reset_on_fork = reset_on_fork;
-               task_rq_unlock(rq, p, &rf);
-               return 0;
+               retval = 0;
+               goto unlock;
        }
 change:
 
@@ -4745,8 +4745,8 @@ change:
                if (rt_bandwidth_enabled() && rt_policy(policy) &&
                                task_group(p)->rt_bandwidth.rt_runtime == 0 &&
                                !task_group_is_autogroup(task_group(p))) {
-                       task_rq_unlock(rq, p, &rf);
-                       return -EPERM;
+                       retval = -EPERM;
+                       goto unlock;
                }
 #endif
 #ifdef CONFIG_SMP
@@ -4761,8 +4761,8 @@ change:
                         */
                        if (!cpumask_subset(span, p->cpus_ptr) ||
                            rq->rd->dl_bw.bw == 0) {
-                               task_rq_unlock(rq, p, &rf);
-                               return -EPERM;
+                               retval = -EPERM;
+                               goto unlock;
                        }
                }
 #endif
@@ -4781,8 +4781,8 @@ change:
         * is available.
         */
        if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
-               task_rq_unlock(rq, p, &rf);
-               return -EBUSY;
+               retval = -EBUSY;
+               goto unlock;
        }
 
        p->sched_reset_on_fork = reset_on_fork;
@@ -4840,6 +4840,10 @@ change:
        preempt_enable();
 
        return 0;
+
+unlock:
+       task_rq_unlock(rq, p, &rf);
+       return retval;
 }
 
 static int _sched_setscheduler(struct task_struct *p, int policy,