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| author | Peter Zijlstra <peterz@infradead.org> | 2013-10-15 10:35:07 (GMT) |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-03-12 12:25:39 (GMT) |
| commit | d171cbfc349b897d89ae4a0fe5fb75c4e1e65097 (patch) | |
| tree | 51266d34689a33178c5e9967366fd97ca1893cb8 /kernel/sched | |
| parent | 4edad9c1129ac6b3ad319009f005d20c6bfda3b9 (diff) | |
| download | linux-fsl-qoriq-d171cbfc349b897d89ae4a0fe5fb75c4e1e65097.tar.xz | |
sched/rt: Add missing rmb()
commit 7c3f2ab7b844f1a859afbc3d41925e8a0faba5fa upstream.
While discussing the proposed SCHED_DEADLINE patches which in parts
mimic the existing FIFO code it was noticed that the wmb in
rt_set_overloaded() didn't have a matching barrier.
The only site using rt_overloaded() to test the rto_count is
pull_rt_task() and we should issue a matching rmb before then assuming
there's an rto_mask bit set.
Without that smp_rmb() in there we could actually miss seeing the
rto_mask bit.
Also, change to using smp_[wr]mb(), even though this is SMP only code;
memory barriers without smp_ always make me think they're against
hardware of some sort.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: vincent.guittot@linaro.org
Cc: luca.abeni@unitn.it
Cc: bruce.ashfield@windriver.com
Cc: dhaval.giani@gmail.com
Cc: rostedt@goodmis.org
Cc: hgu1972@gmail.com
Cc: oleg@redhat.com
Cc: fweisbec@gmail.com
Cc: darren@dvhart.com
Cc: johan.eker@ericsson.com
Cc: p.faure@akatech.ch
Cc: paulmck@linux.vnet.ibm.com
Cc: raistlin@linux.it
Cc: claudio@evidence.eu.com
Cc: insop.song@gmail.com
Cc: michael@amarulasolutions.com
Cc: liming.wang@windriver.com
Cc: fchecconi@gmail.com
Cc: jkacur@redhat.com
Cc: tommaso.cucinotta@sssup.it
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: harald.gustafsson@ericsson.com
Cc: nicola.manica@disi.unitn.it
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/r/20131015103507.GF10651@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/rt.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 417b1b3..0c7886f 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -246,8 +246,10 @@ static inline void rt_set_overload(struct rq *rq) * if we should look at the mask. It would be a shame * if we looked at the mask, but the mask was not * updated yet. + * + * Matched by the barrier in pull_rt_task(). */ - wmb(); + smp_wmb(); atomic_inc(&rq->rd->rto_count); } @@ -1644,6 +1646,12 @@ static int pull_rt_task(struct rq *this_rq) if (likely(!rt_overloaded(this_rq))) return 0; + /* + * Match the barrier from rt_set_overloaded; this guarantees that if we + * see overloaded we must also see the rto_mask bit. + */ + smp_rmb(); + for_each_cpu(cpu, this_rq->rd->rto_mask) { if (this_cpu == cpu) continue; |