Messages in this thread | | | From | "H.J. Lu" <> | Date | Fri, 11 Jan 2019 08:10:33 -0800 | Subject | Re: [patch 1/2] posix-cpu-timers: Unbreak timer rearming |
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On Fri, Jan 11, 2019 at 5:36 AM Thomas Gleixner <tglx@linutronix.de> wrote: > > 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: stable@vger.kernel.org > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: John Stultz <john.stultz@linaro.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, > >
I verified that this patch works on 4.19.14 kernel.
Thanks.
-- H.J.
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