| From 1807ad355ee664864a01facec9859a819cb97113 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 29 Jun 2021 14:14:52 +0200 |
| Subject: sched/fair: Fix CFS bandwidth hrtimer expiry type |
| |
| 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 --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; |
| -- |
| 2.30.2 |
| |