diff mbox series

[5.10,075/125] sched/fair: Fix CFS bandwidth hrtimer expiry type

Message ID 20210722155627.174356109@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman July 22, 2021, 4:31 p.m. UTC 
From: Odin Ugedal <odin@uged.al>

[ Upstream commit 72d0ad7cb5bad265adb2014dbe46c4ccb11afaba ]

The time remaining until expiry of the refresh_timer can be negative.
Casting the type to an unsigned 64-bit value will cause integer
underflow, making the runtime_refresh_within return false instead of
true. These situations are rare, but they do happen.

This does not cause user-facing issues or errors; other than
possibly unthrottling cfs_rq's using runtime from the previous period(s),
making the CFS bandwidth enforcement less strict in those (special)
situations.

Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 32c0905bca84..262b02d75007 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5047,7 +5047,7 @@  static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 {
 	struct hrtimer *refresh_timer = &cfs_b->period_timer;
-	u64 remaining;
+	s64 remaining;
 
 	/* if the call-back is running a quota refresh is already occurring */
 	if (hrtimer_callback_running(refresh_timer))
@@ -5055,7 +5055,7 @@  static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 
 	/* is a quota refresh about to occur? */
 	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
-	if (remaining < min_expire)
+	if (remaining < (s64)min_expire)
 		return 1;
 
 	return 0;