linux-kernel - [tip:timers/core] signals: Use hrtimer for sigtimedwait()

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Date:	Thu, 7 Jul 2016 01:43:58 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	clm@...com, mingo@...nel.org, chrubis@...e.cz, fweisbec@...il.com,
	lenb@...nel.org, arjan@...radead.org,
	torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
	viro@...iv.linux.org.uk, peterz@...radead.org,
	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	josh@...htriplett.org, linux@...encehorizons.net, riel@...hat.com
Subject: [tip:timers/core] signals: Use hrtimer for sigtimedwait()

Commit-ID:  2b1ecc3d1a6b10f8fbac7f83d80db30b5a2c2791
Gitweb:     http://git.kernel.org/tip/2b1ecc3d1a6b10f8fbac7f83d80db30b5a2c2791
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 4 Jul 2016 09:50:25 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 7 Jul 2016 10:35:07 +0200

signals: Use hrtimer for sigtimedwait()

We've converted most timeout related syscalls to hrtimers, but
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@...utronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Arjan van de Ven <arjan@...radead.org>
Cc: Chris Mason <clm@...com>
Cc: Cyril Hrubis <chrubis@...e.cz>
Cc: George Spelvin <linux@...encehorizons.net>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Len Brown <lenb@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: rt@...utronix.de
Link: http://lkml.kernel.org/r/20160704094341.787164909@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/signal.c | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 96e9bc4..af21afc 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2751,23 +2751,18 @@ int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
  *  @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 *which, siginfo_t *info,
 
 	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 *which, siginfo_t *info,
 		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 *which, siginfo_t *info,
 
 	if (sig)
 		return sig;
-	return timeout ? -EINTR : -EAGAIN;
+	return ret ? -EINTR : -EAGAIN;
 }
 
 /**