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posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group

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As of e78c3496790e ("time, signal: Protect resource use statistics
with seqlock") cpu_clock_sample_group no longers needs siglock
protection.  Unfortunately no one realized it at the time.

Remove the extra locking that is for cpu_clock_sample_group and not
for cpu_clock_sample.  This significantly simplifies the code.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/878skmvdts.fsf@x220.int.ebiederm.org
This commit is contained in:
Eric W. Biederman 2020-02-28 11:09:19 -06:00 committed by Thomas Gleixner
parent a2efdbf4fc
commit 60f2ceaa81
1 changed files with 12 additions and 54 deletions
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66
kernel/time/posix-cpu-timers.c
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@ -718,31 +718,10 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
/*
* Sample the clock to take the difference with the expiry time.
*/
if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
if (CPUCLOCK_PERTHREAD(timer->it_clock))
now = cpu_clock_sample(clkid, p);
} else {
struct sighand_struct *sighand;
unsigned long flags;
/*
* Protect against sighand release/switch in exit/exec and
* also make timer sampling safe if it ends up calling
* thread_group_cputime().
*/
sighand = lock_task_sighand(p, &flags);
if (unlikely(sighand == NULL)) {
/*
* The process has been reaped.
* We can't even collect a sample any more.
* Disarm the timer, nothing else to do.
*/
cpu_timer_setexpires(ctmr, 0);
return;
} else {
now = cpu_clock_sample_group(clkid, p, false);
unlock_task_sighand(p, &flags);
}
}
else
now = cpu_clock_sample_group(clkid, p, false);
if (now < expires) {
itp->it_value = ns_to_timespec64(expires - now);
@ -986,43 +965,22 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer)
/*
* Fetch the current sample and update the timer's expiry time.
*/
if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
if (CPUCLOCK_PERTHREAD(timer->it_clock))
now = cpu_clock_sample(clkid, p);
bump_cpu_timer(timer, now);
if (unlikely(p->exit_state))
return;
/* Protect timer list r/w in arm_timer() */
sighand = lock_task_sighand(p, &flags);
if (!sighand)
return;
} else {
/*
* Protect arm_timer() and timer sampling in case of call to
* thread_group_cputime().
*/
sighand = lock_task_sighand(p, &flags);
if (unlikely(sighand == NULL)) {
/*
* The process has been reaped.
* We can't even collect a sample any more.
*/
cpu_timer_setexpires(ctmr, 0);
return;
} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
/* If the process is dying, no need to rearm */
goto unlock;
}
else
now = cpu_clock_sample_group(clkid, p, true);
bump_cpu_timer(timer, now);
/* Leave the sighand locked for the call below. */
}
bump_cpu_timer(timer, now);
/* Protect timer list r/w in arm_timer() */
sighand = lock_task_sighand(p, &flags);
if (unlikely(sighand == NULL))
return;
/*
* Now re-arm for the new expiry time.
*/
arm_timer(timer);
unlock:
unlock_task_sighand(p, &flags);
}