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Subject[patch 4 10/22] signal: Use hrtimer for sigtimedwait
We've converted most timeout related syscalls to hrtimers. sigtimedwait() did
not get this treatment. Convert it so we get a reasonable accuracy and remove
the user space exposure to the timer wheel properties.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Cyril Hrubis <chrubis@suse.cz>
---
kernel/signal.c | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2751,23 +2751,18 @@ int copy_siginfo_to_user(siginfo_t __use
* @ts: upper bound on process time suspension
*/
int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
- const struct timespec *ts)
+ const struct timespec *ts)
{
+ ktime_t *to = NULL, timeout = { .tv64 = KTIME_MAX };
struct task_struct *tsk = current;
- long timeout = MAX_SCHEDULE_TIMEOUT;
sigset_t mask = *which;
- int sig;
+ int sig, ret = 0;

if (ts) {
if (!timespec_valid(ts))
return -EINVAL;
- timeout = timespec_to_jiffies(ts);
- /*
- * We can be close to the next tick, add another one
- * to ensure we will wait at least the time asked for.
- */
- if (ts->tv_sec || ts->tv_nsec)
- timeout++;
+ timeout = timespec_to_ktime(*ts);
+ to = &timeout;
}

/*
@@ -2778,7 +2773,7 @@ int do_sigtimedwait(const sigset_t *whic

spin_lock_irq(&tsk->sighand->siglock);
sig = dequeue_signal(tsk, &mask, info);
- if (!sig && timeout) {
+ if (!sig && timeout.tv64) {
/*
* None ready, temporarily unblock those we're interested
* while we are sleeping in so that we'll be awakened when
@@ -2790,8 +2785,9 @@ int do_sigtimedwait(const sigset_t *whic
recalc_sigpending();
spin_unlock_irq(&tsk->sighand->siglock);

- timeout = freezable_schedule_timeout_interruptible(timeout);
-
+ __set_current_state(TASK_INTERRUPTIBLE);
+ ret = freezable_schedule_hrtimeout_range(to, tsk->timer_slack_ns,
+ HRTIMER_MODE_REL);
spin_lock_irq(&tsk->sighand->siglock);
__set_task_blocked(tsk, &tsk->real_blocked);
sigemptyset(&tsk->real_blocked);
@@ -2801,7 +2797,7 @@ int do_sigtimedwait(const sigset_t *whic

if (sig)
return sig;
- return timeout ? -EINTR : -EAGAIN;
+ return ret ? -EINTR : -EAGAIN;
}

/**

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