diff options
| author | Ben Segall <bsegall@google.com> | 2013-10-16 11:16:32 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-01-03 04:33:31 +0000 |
| commit | 49c5317fa0fa5d0dfa5d15dc3010e2578beddb16 (patch) | |
| tree | 29f9954b3ed112d821cf42b8041dc60bb3372a09 /kernel | |
| parent | dae9d455d193fd2bc03fca65d255053f4debf8aa (diff) | |
sched: Avoid throttle_cfs_rq() racing with period_timer stopping
commit f9f9ffc237dd924f048204e8799da74f9ecf40cf upstream.
throttle_cfs_rq() doesn't check to make sure that period_timer is running,
and while update_curr/assign_cfs_runtime does, a concurrently running
period_timer on another cpu could cancel itself between this cpu's
update_curr and throttle_cfs_rq(). If there are no other cfs_rqs running
in the tg to restart the timer, this causes the cfs_rq to be stranded
forever.
Fix this by calling __start_cfs_bandwidth() in throttle if the timer is
inactive.
(Also add some sched_debug lines for cfs_bandwidth.)
Tested: make a run/sleep task in a cgroup, loop switching the cgroup
between 1ms/100ms quota and unlimited, checking for timer_active=0 and
throttled=1 as a failure. With the throttle_cfs_rq() change commented out
this fails, with the full patch it passes.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2: adjust filenames]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched_debug.c | 8 | ||||
| -rw-r--r-- | kernel/sched_fair.c | 2 |
2 files changed, 10 insertions, 0 deletions
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index a6710a112b4..f4010e2820f 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -213,6 +213,14 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) SEQ_printf(m, " .%-30s: %d\n", "load_tg", atomic_read(&cfs_rq->tg->load_weight)); #endif +#ifdef CONFIG_CFS_BANDWIDTH + SEQ_printf(m, " .%-30s: %d\n", "tg->cfs_bandwidth.timer_active", + cfs_rq->tg->cfs_bandwidth.timer_active); + SEQ_printf(m, " .%-30s: %d\n", "throttled", + cfs_rq->throttled); + SEQ_printf(m, " .%-30s: %d\n", "throttle_count", + cfs_rq->throttle_count); +#endif print_cfs_group_stats(m, cpu, cfs_rq->tg); #endif diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index c261da7ddc7..5b9e456ea98 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1527,6 +1527,8 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq) cfs_rq->throttled_timestamp = rq->clock; raw_spin_lock(&cfs_b->lock); list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); + if (!cfs_b->timer_active) + __start_cfs_bandwidth(cfs_b); raw_spin_unlock(&cfs_b->lock); } |