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cfq_idle_class_timer: add paranoid checks for jiffies overflow

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In theory, if the queue was idle long enough, cfq_idle_class_timer may have
a false (and very long) timeout because jiffies can wrap into the past wrt
->last_end_request.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Oleg Nesterov 2007-11-07 13:51:35 +01:00 committed by Jens Axboe
parent b70c864d3c
commit 0e7be9edb9
1 changed files with 17 additions and 11 deletions
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28
block/cfq-iosched.c
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@ -789,6 +789,20 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
__cfq_slice_expired(cfqd, cfqq, timed_out);
}
static int start_idle_class_timer(struct cfq_data *cfqd)
{
unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
unsigned long now = jiffies;
if (time_before(now, end) &&
time_after_eq(now, cfqd->last_end_request)) {
mod_timer(&cfqd->idle_class_timer, end);
return 1;
}
return 0;
}
/*
* Get next queue for service. Unless we have a queue preemption,
* we'll simply select the first cfqq in the service tree.
@ -805,19 +819,14 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
cfqq = rb_entry(n, struct cfq_queue, rb_node);
if (cfq_class_idle(cfqq)) {
unsigned long end;
/*
* if we have idle queues and no rt or be queues had
* pending requests, either allow immediate service if
* the grace period has passed or arm the idle grace
* timer
*/
end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (time_before(jiffies, end)) {
mod_timer(&cfqd->idle_class_timer, end);
if (start_idle_class_timer(cfqd))
cfqq = NULL;
}
}
return cfqq;
@ -2036,17 +2045,14 @@ static void cfq_idle_slice_timer(unsigned long data)
static void cfq_idle_class_timer(unsigned long data)
{
struct cfq_data *cfqd = (struct cfq_data *) data;
unsigned long flags, end;
unsigned long flags;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
/*
* race with a non-idle queue, reset timer
*/
end = cfqd->last_end_request + CFQ_IDLE_GRACE;
if (!time_after_eq(jiffies, end))
mod_timer(&cfqd->idle_class_timer, end);
else
if (!start_idle_class_timer(cfqd))
cfq_schedule_dispatch(cfqd);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);