Re: [Xenomai] [Xenomai-git] Jan Kiszka : cobalt/timer: Make xntimer_get_overruns robust against stopped timers

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On Wed, Feb 24, 2016 at 10:07:47PM +0100, git repository hosting wrote:
> Module: xenomai-jki
> Branch: for-forge
> Commit: 8e6d76e07af74056f6cb4d8cfb192485d07732f7
> URL:    http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=8e6d76e07af74056f6cb4d8cfb192485d07732f7
> 
> Author: Jan Kiszka <jan.kiszka@siemens.com>
> Date:   Wed Feb 24 21:44:41 2016 +0100
> 
> cobalt/timer: Make xntimer_get_overruns robust against stopped timers
> 
> xntimer_get_overruns might be called on meanwhile stopped timers,
> specifically by cobalt_timer_deliver. We crash if we try to dequeue a
> stopped timer, and we should not restart it as well.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> 
> ---
> 
>  kernel/cobalt/timer.c |   14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/cobalt/timer.c b/kernel/cobalt/timer.c
> index db6263d..3e85a53 100644
> --- a/kernel/cobalt/timer.c
> +++ b/kernel/cobalt/timer.c
> @@ -602,13 +602,15 @@ unsigned long long xntimer_get_overruns(struct xntimer *timer, xnticks_t now)
>  		overruns = xnarch_div64(delta, period);
>  		timer->pexpect_ticks += overruns;
>  
> -		q = xntimer_percpu_queue(timer);
> -		xntimer_dequeue(timer, q);
> -		while (xntimerh_date(&timer->aplink) < now) {
> -			timer->periodic_ticks++;
> -			xntimer_update_date(timer);
> +		if (xntimer_running_p(timer)) {
> +			q = xntimer_percpu_queue(timer);
> +			xntimer_dequeue(timer, q);
> +			while (xntimerh_date(&timer->aplink) < now) {
> +				timer->periodic_ticks++;
> +				xntimer_update_date(timer);
> +			}
> +			xntimer_enqueue_and_program(timer, q);
>  		}
> -		xntimer_enqueue_and_program(timer, q);

This looks wrong. xntimer_get_overruns should not be called on a
stopped timer. We want the caller to return an error if called on a
stopped timer, not the condition being silently ignored.

-- 
					    Gilles.
https://click-hack.org