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authorBen Segall <bsegall@google.com>2013-10-16 11:16:17 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-15 15:28:54 -0800
commit373e0a593bd15df79e47158bd4628eb133d4da7d (patch)
tree55f333dc067726fbb4f11338f1ca09d1bb6d43b2
parent9d80092f8d9e0fc4aa2b6a7c8d2e4a7437899ca5 (diff)
downloadlinaro-lsk-373e0a593bd15df79e47158bd4628eb133d4da7d.tar.gz
sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining
commit db06e78cc13d70f10877e0557becc88ab3ad2be8 upstream. hrtimer_expires_remaining does not take internal hrtimer locks and thus must be guarded against concurrent __hrtimer_start_range_ns (but returning HRTIMER_RESTART is safe). Use cfs_b->lock to make it safe. 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/20131016181617.22647.73829.stgit@sword-of-the-dawn.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Chris J Arges <chris.j.arges@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/sched/fair.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 54e85898c39..d0a7b93ce05 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2470,7 +2470,13 @@ static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
-/* are we near the end of the current quota period? */
+/*
+ * Are we near the end of the current quota period?
+ *
+ * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
+ * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
+ * migrate_hrtimers, base is never cleared, so we are fine.
+ */
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
struct hrtimer *refresh_timer = &cfs_b->period_timer;
@@ -2546,10 +2552,12 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
u64 expires;
/* confirm we're still not at a refresh boundary */
- if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
+ raw_spin_lock(&cfs_b->lock);
+ if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
+ raw_spin_unlock(&cfs_b->lock);
return;
+ }
- raw_spin_lock(&cfs_b->lock);
if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
runtime = cfs_b->runtime;
cfs_b->runtime = 0;