linux-kernel - [PATCH 6/2] posix-cpu-timers: timer functions must use timer time instead of clock time

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Message-ID: <517EC806.6040403@gmail.com>
Date:	Mon, 29 Apr 2013 15:20:38 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	linux-kernel@...r.kernel.org
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Olivier Langlois <olivier@...llion01.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	kosaki.motohiro@...il.com
Subject: [PATCH 6/2] posix-cpu-timers: timer functions must use timer time
 instead of clock time

For process timer, we use cpu_clock_sample_group() and cpu_timer_sample_group
correctly. However for thread timer, we always use cpu_clock_sample().
That's wrong becuase cpu_clock_sample() account uncommited delta_exec too.

This is not big matter because following workaround code in
posix_cpu_timer_get() hide the timer inversion issue. However it makes wrong
rq lock held and would be better to fix.

  if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
    ...
  } else {
    /*
     * The timer should have expired already, but the firing
     * hasn't taken place yet.  Say it's just about to expire.
     */
     itp->it_value.tv_nsec = 1;
     itp->it_value.tv_sec = 0;

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 kernel/posix-cpu-timers.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9088023..472394b 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -700,7 +700,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 	 * check if it's already passed.  In short, we need a sample.
 	 */
 	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
-		do_cpu_clock_sample(timer->it_clock, p, false, &val);
+		cpu_timer_sample(timer->it_clock, p, &val);
 	} else {
 		cpu_timer_sample_group(timer->it_clock, p, &val);
 	}
@@ -840,7 +840,7 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 	 * Sample the clock to take the difference with the expiry time.
 	 */
 	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
-		cpu_clock_sample(timer->it_clock, p, &now);
+		cpu_timer_sample(timer->it_clock, p, &now);
 		clear_dead = p->exit_state;
 	} else {
 		read_lock(&tasklist_lock);
@@ -1165,7 +1165,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 	 * Fetch the current sample and update the timer's expiry time.
 	 */
 	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
-		cpu_clock_sample(timer->it_clock, p, &now);
+		cpu_timer_sample(timer->it_clock, p, &now);
 		bump_cpu_timer(timer, now);
 		if (unlikely(p->exit_state)) {
 			clear_dead_task(timer, now);
-- 
1.7.1


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