[patch 2/4] timerfd: Handle relative timers with CONFIG_TIME_LOW_RES proper

From: Thomas Gleixner
Date: Thu Jan 14 2016 - 11:55:50 EST


Helge reported that a relative timer can return a remaining time larger than
the programmed relative time on parisc and other architectures which have
CONFIG_TIME_LOW_RES set. This happens because we add a jiffie to the resulting
expiry time to prevent short timeouts.

Use the new function hrtimer_expires_remaining_adjusted() to calculate the
remaining time. It takes that extra added time into account for relative
timers.

Reported-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
fs/timerfd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -153,7 +153,7 @@ static ktime_t timerfd_get_remaining(str
if (isalarm(ctx))
remaining = alarm_expires_remaining(&ctx->t.alarm);
else
- remaining = hrtimer_expires_remaining(&ctx->t.tmr);
+ remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);

return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
}