===================================================================
@@ -494,7 +494,6 @@ static void cbq_ovl_delay(struct cbq_cla
if (!cl->delayed) {
psched_time_t sched = q->now;
- ktime_t expires;
delay += cl->offtime;
if (cl->avgidle < 0)
@@ -504,6 +503,7 @@ static void cbq_ovl_delay(struct cbq_cla
cl->undertime = q->now + delay;
if (delay > 0) {
+ ktime_t expires, actexp;
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
@@ -514,12 +514,19 @@ static void cbq_ovl_delay(struct cbq_cla
expires = ktime_set(0, 0);
expires = ktime_add_ns(expires, PSCHED_TICKS2NS(sched));
- if (hrtimer_try_to_cancel(&q->delay_timer) &&
- ktime_to_ns(ktime_sub(
- hrtimer_get_expires(&q->delay_timer),
- expires)) > 0)
- hrtimer_set_expires(&q->delay_timer, expires);
- hrtimer_restart(&q->delay_timer);
+ /*
+ * If the timer is queued check whether the
+ * new expiry time is earlier than the current
+ * one.
+ */
+ if (hrtimer_is_queued(&q->delay_timer)) {
+ actexp = hrtimer_get_expires(&q->delay_timer);
+ if (expires.tv64 >= actexp.tv64)
+ expires.tv64 = 0;
+ }
+ if (expires.tv64)
+ hrtimer_start(&q->delay_timer, expires,
+ HRTIMER_MODE_ABS);
cl->delayed = 1;
cl->xstats.overactions++;
spin_unlock_irqrestore(&q->lock, flags);
The usage of hrtimer in cbq_ovl_delay() is less than obvious and in two aspects wrong. The intention of the code is to arm an hrtimer with the expiry time X. If the timer is already armed the code needs to check whether the expiry time X is earlier than the expiry time of the armed timer and either keep the active timer or rearm it to X. If the timer is not armed it needs to schedule it to X. That's not what the code does. It calls hrtimer_try_to_cancel() unconditionally and checks the return value. If the return value is non zero then it compares the expiry time of the timer with the new expiry time and picks the earlier one. The return value check does not take into account that the timer might run its callback (expressed by a return value of -1). In that case the expiry time of the timer is probably earlier than the new expiry time so it rearms the already expired timer with the expiry value in the past. If the timer is not active (hrtimer_try_to_cancel() returns 0) it does not set the new expiry time X but instead restarts the timer with the expiry time which was active when the timer fired last. That's in the past as well. Change the code to check whether the timer is enqueued. If it is enqueued then the expiry time of the timer is checked against the new expiry time and it only calls hrtimer_start when the new expiry time is earlier than the already armed timer. If the timer is not active then arm it unconditionally with the new expiry time. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Patrick McHardy <kaber@trash.net> --- net/sched/sch_cbq.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html