提交 72d0ad7c 编写于 作者: O Odin Ugedal 提交者: Peter Zijlstra

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: NOdin Ugedal <odin@uged.al>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NBen Segall <bsegall@google.com>
Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al
上级 ceb6ba45
...@@ -5054,7 +5054,7 @@ static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; ...@@ -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) static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{ {
struct hrtimer *refresh_timer = &cfs_b->period_timer; 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 the call-back is running a quota refresh is already occurring */
if (hrtimer_callback_running(refresh_timer)) if (hrtimer_callback_running(refresh_timer))
...@@ -5062,7 +5062,7 @@ static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) ...@@ -5062,7 +5062,7 @@ static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
/* is a quota refresh about to occur? */ /* is a quota refresh about to occur? */
remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
if (remaining < min_expire) if (remaining < (s64)min_expire)
return 1; return 1;
return 0; return 0;
......
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