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Re: [PATCH v2 1/2] posix-timers: Prevents overrun counter overflow
- From: Thomas Gleixner <tglx at linutronix dot de>
- To: Daniel Church <dchurch at andplus dot com>
- Cc: linux-kernel at vger dot kernel dot org, libc-alpha at sourceware dot org
- Date: Sat, 24 Jan 2015 20:14:45 +0100 (CET)
- Subject: Re: [PATCH v2 1/2] posix-timers: Prevents overrun counter overflow
- Authentication-results: sourceware.org; auth=none
- References: <[PATCH 0/2] posix-timers: Prevents overrun counter overflow, adds DELAYTIMER_MAX> <1422121737-3686-1-git-send-email-dchurch at andplus dot com> <1422121737-3686-2-git-send-email-dchurch at andplus dot com>
On Sat, 24 Jan 2015, Daniel Church wrote:
> +/*
> + * Updates a timer's overrun count while capping it to delaytimer_max
> + */
> +static void posix_timer_update_overrun_count(struct k_itimer *timer,
> + unsigned int overruns)
> +{
> + const bool newOverrunsAboveMax = overruns >= delaytimer_max;
> + const bool totalOverrunsAboveMax =
> + timer->it_overrun >= 0 &&
> + timer->it_overrun >= delaytimer_max - overruns;
No CaMelCaSe please. And the const here is pointless.
Aside of that in a function like this we really want short local
variables so we can avoid the horrible to read multi line code.
> + if (newOverrunsAboveMax || totalOverrunsAboveMax) {
> + timer->it_overrun = delaytimer_max;
> + } else {
> + timer->it_overrun += overruns;
> + }
> +}
> +
> /* Get clock_realtime */
> static int posix_clock_realtime_get(clockid_t which_clock, struct timespec *tp)
> {
> @@ -350,14 +370,17 @@ __initcall(init_posix_timers);
>
> static void schedule_next_timer(struct k_itimer *timr)
> {
> + unsigned int overruns;
> struct hrtimer *timer = &timr->it.real.timer;
>
> if (timr->it.real.interval.tv64 == 0)
> return;
>
> - timr->it_overrun += (unsigned int) hrtimer_forward(timer,
> - timer->base->get_time(),
> - timr->it.real.interval);
> + overruns = (unsigned int) hrtimer_forward(timer,
> + timer->base->get_time(),
> + timr->it.real.interval);
Why not:
posix_timer_forward(struct hrtimer *hrt, struct k_itimer *tmr)
and doing the forward there as well? The now optimization in
common_timer_get is not that important and if we really want to keep
it, we can hand in a pointer and read the time in the function if the
pointer is NULL.
Thanks,
tglx