| From 93ad0fc088c5b4631f796c995bdd27a082ef33a6 Mon Sep 17 00:00:00 2001 |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Fri, 11 Jan 2019 14:33:16 +0100 |
| Subject: posix-cpu-timers: Unbreak timer rearming |
| |
| From: Thomas Gleixner <tglx@linutronix.de> |
| |
| commit 93ad0fc088c5b4631f796c995bdd27a082ef33a6 upstream. |
| |
| The recent commit which prevented a division by 0 issue in the alarm timer |
| code broke posix CPU timers as an unwanted side effect. |
| |
| The reason is that the common rearm code checks for timer->it_interval |
| being 0 now. What went unnoticed is that the posix cpu timer setup does not |
| initialize timer->it_interval as it stores the interval in CPU timer |
| specific storage. The reason for the separate storage is historical as the |
| posix CPU timers always had a 64bit nanoseconds representation internally |
| while timer->it_interval is type ktime_t which used to be a modified |
| timespec representation on 32bit machines. |
| |
| Instead of reverting the offending commit and fixing the alarmtimer issue |
| in the alarmtimer code, store the interval in timer->it_interval at CPU |
| timer setup time so the common code check works. This also repairs the |
| existing inconistency of the posix CPU timer code which kept a single shot |
| timer armed despite of the interval being 0. |
| |
| The separate storage can be removed in mainline, but that needs to be a |
| separate commit as the current one has to be backported to stable kernels. |
| |
| Fixes: 0e334db6bb4b ("posix-timers: Fix division by zero bug") |
| Reported-by: H.J. Lu <hjl.tools@gmail.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Cc: John Stultz <john.stultz@linaro.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: stable@vger.kernel.org |
| Link: https://lkml.kernel.org/r/20190111133500.840117406@linutronix.de |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/time/posix-cpu-timers.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/kernel/time/posix-cpu-timers.c |
| +++ b/kernel/time/posix-cpu-timers.c |
| @@ -685,6 +685,7 @@ static int posix_cpu_timer_set(struct k_ |
| * set up the signal and overrun bookkeeping. |
| */ |
| timer->it.cpu.incr = timespec64_to_ns(&new->it_interval); |
| + timer->it_interval = ns_to_ktime(timer->it.cpu.incr); |
| |
| /* |
| * This acts as a modification timestamp for the timer, |