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sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining 

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>
This commit is contained in:
Ben Segall 2013-10-16 11:16:17 -07:00 committed by Ingo Molnar
parent 1ee14e6c8c
commit db06e78cc1
1 changed files with 12 additions and 4 deletions
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16
kernel/sched/fair.c
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@ -3285,7 +3285,13 @@ 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;
@ -3361,10 +3367,12 @@ 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))
return;
raw_spin_lock(&cfs_b->lock);
if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
raw_spin_unlock(&cfs_b->lock);
return;
}
if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
runtime = cfs_b->runtime;
cfs_b->runtime = 0;