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Commit db06e78c authored by Ben Segall's avatar Ben Segall Committed by Ingo Molnar
Browse files

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: default avatarBen Segall <bsegall@google.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 1ee14e6c

kernel/sched/fair.c

+11 −3
Original line number Diff line number Diff line
@@ -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))

	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;