The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 72d0ad7cb5bad265adb2014dbe46c4ccb11afaba
Gitweb: https://git.kernel.org/tip/72d0ad7cb5bad265adb2014dbe46c4ccb11afaba
Author: Odin Ugedal <odin@xxxxxxx>
AuthorDate: Tue, 29 Jun 2021 14:14:52 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 02 Jul 2021 15:58:24 +02:00
sched/fair: Fix CFS bandwidth hrtimer expiry type
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@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Ben Segall <bsegall@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@xxxxxxx
---
kernel/sched/fair.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1e263c9..1b15a19 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5054,7 +5054,7 @@ 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))
@@ -5062,7 +5062,7 @@ 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;
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