Thomas Gleixner <tglx@linutronix.de> writes:
> In preparation for addressing issues in the timer_get() and timer_set()
> functions of posix CPU timers.
To see that this was safe I had to lookup and see that
cpu_timer_getexpires is a truly trivial function.
static inline u64 cpu_timer_getexpires(struct cpu_timer *ctmr)
{
return ctmr->node.expires;
}
I am a bit confused by the purpose of this function in
posix-cpu-timers.c. In some places this helper is used (like below),
and in other places like bump_cpu_timer the expires member is
accessed directly.
It isn't really a problem, but it is something that might be
worth making consistent in the code to make it easier to read.
Eric
> No functional change.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> V2: Split out into new patch to make review simpler - Frederic
> ---
> kernel/time/posix-cpu-timers.c | 51 +++++++++++++++++++----------------------
> 1 file changed, 24 insertions(+), 27 deletions(-)
>
> --- a/kernel/time/posix-cpu-timers.c
> +++ b/kernel/time/posix-cpu-timers.c
> @@ -785,33 +785,9 @@ static int posix_cpu_timer_set(struct k_
> return ret;
> }
>
> -static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
> +static void __posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp, u64 now)
> {
> - clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
> - struct cpu_timer *ctmr = &timer->it.cpu;
> - u64 now, expires = cpu_timer_getexpires(ctmr);
> - struct task_struct *p;
> -
> - rcu_read_lock();
> - p = cpu_timer_task_rcu(timer);
> - if (!p)
> - goto out;
> -
> - /*
> - * Easy part: convert the reload time.
> - */
> - itp->it_interval = ktime_to_timespec64(timer->it_interval);
> -
> - if (!expires)
> - goto out;
> -
> - /*
> - * Sample the clock to take the difference with the expiry time.
> - */
> - if (CPUCLOCK_PERTHREAD(timer->it_clock))
> - now = cpu_clock_sample(clkid, p);
> - else
> - now = cpu_clock_sample_group(clkid, p, false);
> + u64 expires = cpu_timer_getexpires(&timer->it.cpu);
>
> if (now < expires) {
> itp->it_value = ns_to_timespec64(expires - now);
> @@ -823,7 +799,28 @@ static void posix_cpu_timer_get(struct k
> itp->it_value.tv_nsec = 1;
> itp->it_value.tv_sec = 0;
> }
> -out:
> +}
> +
> +static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
> +{
> + clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
> + struct task_struct *p;
> + u64 now;
> +
> + rcu_read_lock();
> + p = cpu_timer_task_rcu(timer);
> + if (p) {
> + itp->it_interval = ktime_to_timespec64(timer->it_interval);
> +
> + if (cpu_timer_getexpires(&timer->it.cpu)) {
> + if (CPUCLOCK_PERTHREAD(timer->it_clock))
> + now = cpu_clock_sample(clkid, p);
> + else
> + now = cpu_clock_sample_group(clkid, p, false);
> +
> + __posix_cpu_timer_get(timer, itp, now);
> + }
> + }
> rcu_read_unlock();
> }
>