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authorOleg Nesterov <oleg@tv-sign.ru>2007-11-07 13:51:35 +0100
committerJens Axboe <jens.axboe@oracle.com>2007-11-07 13:51:35 +0100
commit0e7be9edb9134f833278c381b6feabb54b875208 (patch)
treea4eca4110f1b672f78191c8a8f92086b1b6ade7a /block/cfq-iosched.c
parentb70c864d3ce706571d2f3cac1d35d4fba01d6072 (diff)
downloadconfigs-0e7be9edb9134f833278c381b6feabb54b875208.tar.gz
cfq_idle_class_timer: add paranoid checks for jiffies overflow
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>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c28
1 files changed, 17 insertions, 11 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 6831a758d54..0b4a4790557 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -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 @@ out_cont:
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);