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Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull timer fix from Ingo Molnar:
 "Fix a timer expiry bug that would cause spurious delay of timers"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timer: Read jiffies once when forwarding base clk
This commit is contained in:
Linus Torvalds 2019-09-26 15:53:17 -07:00
commit da05b5ea12
1 changed files with 5 additions and 3 deletions
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8
kernel/time/timer.c
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@ -1678,24 +1678,26 @@ void timer_clear_idle(void)
static int collect_expired_timers(struct timer_base *base,
struct hlist_head *heads)
{
unsigned long now = READ_ONCE(jiffies);
/*
* NOHZ optimization. After a long idle sleep we need to forward the
* base to current jiffies. Avoid a loop by searching the bitfield for
* the next expiring timer.
*/
if ((long)(jiffies - base->clk) > 2) {
if ((long)(now - base->clk) > 2) {
unsigned long next = __next_timer_interrupt(base);
/*
* If the next timer is ahead of time forward to current
* jiffies, otherwise forward to the next expiry time:
*/
if (time_after(next, jiffies)) {
if (time_after(next, now)) {
/*
* The call site will increment base->clk and then
* terminate the expiry loop immediately.
*/
base->clk = jiffies;
base->clk = now;
return 0;
}
base->clk = next;