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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-04-05 17:23:46 +0200
committerIngo Molnar <mingo@elte.hu>2011-04-14 08:52:36 +0200
commit7608dec2ce2004c234339bef8c8074e5e601d0e9 (patch)
treea855754a4fa3de6fe0d287c9d94d58d7bd6e8978 /kernel/sched_rt.c
parent013fdb8086acaae5f8eb96f9ad48fcd98882ac46 (diff)
sched: Drop the rq argument to sched_class::select_task_rq()
In preparation of calling select_task_rq() without rq->lock held, drop the dependency on the rq argument. Reviewed-by: Frank Rowand <frank.rowand@am.sony.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110405152729.031077745@chello.nl Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_rt.c')
-rw-r--r--kernel/sched_rt.c38
1 files changed, 26 insertions, 12 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9ca4f5f879c..19ecb312737 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -977,13 +977,23 @@ static void yield_task_rt(struct rq *rq)
static int find_lowest_rq(struct task_struct *task);
static int
-select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
+select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
{
+ struct task_struct *curr;
+ struct rq *rq;
+ int cpu;
+
if (sd_flag != SD_BALANCE_WAKE)
return smp_processor_id();
+ cpu = task_cpu(p);
+ rq = cpu_rq(cpu);
+
+ rcu_read_lock();
+ curr = ACCESS_ONCE(rq->curr); /* unlocked access */
+
/*
- * If the current task is an RT task, then
+ * If the current task on @p's runqueue is an RT task, then
* try to see if we can wake this RT task up on another
* runqueue. Otherwise simply start this RT task
* on its current runqueue.
@@ -997,21 +1007,25 @@ select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
* lock?
*
* For equal prio tasks, we just let the scheduler sort it out.
+ *
+ * Otherwise, just let it ride on the affined RQ and the
+ * post-schedule router will push the preempted task away
+ *
+ * This test is optimistic, if we get it wrong the load-balancer
+ * will have to sort it out.
*/
- if (unlikely(rt_task(rq->curr)) &&
- (rq->curr->rt.nr_cpus_allowed < 2 ||
- rq->curr->prio < p->prio) &&
+ if (curr && unlikely(rt_task(curr)) &&
+ (curr->rt.nr_cpus_allowed < 2 ||
+ curr->prio < p->prio) &&
(p->rt.nr_cpus_allowed > 1)) {
- int cpu = find_lowest_rq(p);
+ int target = find_lowest_rq(p);
- return (cpu == -1) ? task_cpu(p) : cpu;
+ if (target != -1)
+ cpu = target;
}
+ rcu_read_unlock();
- /*
- * Otherwise, just let it ride on the affined RQ and the
- * post-schedule router will push the preempted task away
- */
- return task_cpu(p);
+ return cpu;
}
static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)