linux-kernel - Re: [GIT PULL] timer fix

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Date:   Sun, 23 Dec 2018 20:29:26 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] timer fix

On Fri, Dec 21, 2018 at 01:34:53PM +0100, Ingo Molnar wrote:
> Linus,
> 
> Please pull the latest timers-urgent-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus
> 
>    # HEAD: 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94 posix-timers: Fix division by zero bug
> 
> Fix a division by zero crash in the posix-timers code.
> 
>  Thanks,
> 
> 	Ingo
> 
> ------------------>
> Thomas Gleixner (1):
>       posix-timers: Fix division by zero bug
> 
> 
>  kernel/time/posix-timers.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
> index bd62b5eeb5a0..31f49ae80f43 100644
> --- a/kernel/time/posix-timers.c
> +++ b/kernel/time/posix-timers.c
> @@ -289,9 +289,6 @@ static void common_hrtimer_rearm(struct k_itimer *timr)
>  {
>  	struct hrtimer *timer = &timr->it.real.timer;
>  
> -	if (!timr->it_interval)
> -		return;
> -
>  	timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(),
>  					    timr->it_interval);
>  	hrtimer_restart(timer);
> @@ -317,7 +314,7 @@ void posixtimer_rearm(struct kernel_siginfo *info)
>  	if (!timr)
>  		return;
>  
> -	if (timr->it_requeue_pending == info->si_sys_private) {
> +	if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) {
>  		timr->kclock->timer_rearm(timr);

FWIW, with this patch the vanilla glibc 2.28 self tests
rt/tst-cputimer1, rt/tst-cputimer2, and rt/tst-cputimer3
start to fail on s390:

rt/tst-cputimer1.out:
clock_gettime returned timespec = { 0, 117181 }
clock_getres returned timespec = { 0, 1 }
Timed out: killed the child process
rt/tst-cputimer1.test-result:
FAIL: rt/tst-cputimer1
original exit status 1

rt/tst-cputimer2.out:
clock_gettime returned timespec = { 0, 9686 }
clock_getres returned timespec = { 0, 1 }
Timed out: killed the child process
rt/tst-cputimer2.test-result:
FAIL: rt/tst-cputimer2
original exit status 1

rt/tst-cputimer3.out:
clock_gettime returned timespec = { 0, 0 }
clock_getres returned timespec = { 0, 1 }
Timed out: killed the child process
rt/tst-cputimer3.test-result:
FAIL: rt/tst-cputimer3
original exit status 1

I haven't looked any further into this, just reporting.. otherwise the
test systems seem to be healthy.