This is a note to let you know that I've just added the patch titled
sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fix-cfs_bandwidth-misuse-of-hrtimer_expires_remaining.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From db06e78cc13d70f10877e0557becc88ab3ad2be8 Mon Sep 17 00:00:00 2001
From: Ben Segall <bsegall@xxxxxxxxxx>
Date: Wed, 16 Oct 2013 11:16:17 -0700
Subject: sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining
From: Ben Segall <bsegall@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: pjt@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20131016181617.22647.73829.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Chris J Arges <chris.j.arges@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2519,7 +2519,13 @@ static const u64 min_bandwidth_expiratio
/* 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;
@@ -2595,10 +2601,12 @@ static void do_sched_cfs_slack_timer(str
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;
Patches currently in stable-queue which might be from bsegall@xxxxxxxxxx are
queue-3.12/sched-fix-hrtimer_cancel-rq-lock-deadlock.patch
queue-3.12/sched-fix-cfs_bandwidth-misuse-of-hrtimer_expires_remaining.patch
queue-3.12/sched-fix-race-on-toggling-cfs_bandwidth_used.patch
--
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