[GIT PULL] posix cpu timers updates

[GIT PULL] posix cpu timers updates

[Frederic Weisbecker]

Thomas,

Please pull the timers/posix-cpu-timers-for-tglx branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	timers/posix-cpu-timers-for-tglx

Most of these patches have been hanging around for several month now, in -mmotm
for a significant chunk. They already missed a few releases.

This pile includes quite a part of these. Kosaki also has some pending patches
that we are still discussing a bit. But I'll try to take care of these as well.

Thanks,
	Frederic
---

Frederic Weisbecker (6):
      posix_cpu_timer: consolidate expiry time type
      posix_cpu_timers: consolidate timer list cleanups
      posix_cpu_timers: consolidate expired timers check
      selftests: add basic posix timers selftests
      posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()
      posix_timers: fix racy timer delta caching on task exit

KOSAKI Motohiro (1):
      posix-cpu-timers: don't account cpu timer after stopped thread runtime accounting


 include/linux/posix-timers.h                  |   16 +-
 kernel/posix-cpu-timers.c                     |  395 +++++++++----------------
 kernel/sched/stats.h                          |   39 +++-
 tools/testing/selftests/Makefile              |    1 +
 tools/testing/selftests/timers/Makefile       |    8 +
 tools/testing/selftests/timers/posix_timers.c |  221 ++++++++++++++
 6 files changed, 417 insertions(+), 263 deletions(-)

[PATCH 1/7] posix_cpu_timer: consolidate expiry time type

[Frederic Weisbecker]

The posix cpu timer expiry time is stored in a union of two types: a 64
bits field if we rely on scheduler precise accounting, or a cputime_t if
we rely on jiffies.

This results in quite some duplicate code and special cases to handle the
two types.

Just unify this into a single 64 bits field.  cputime_t can always fit
into it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/posix-timers.h |   16 ++-
 kernel/posix-cpu-timers.c    |  266 +++++++++++++++++-------------------------
 2 files changed, 117 insertions(+), 165 deletions(-)

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 7794d75..907f3fd 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -7,14 +7,20 @@
 #include <linux/timex.h>
 #include <linux/alarmtimer.h>
 
-union cpu_time_count {
-	cputime_t cpu;
-	unsigned long long sched;
-};
+
+static inline unsigned long long cputime_to_expires(cputime_t expires)
+{
+	return (__force unsigned long long)expires;
+}
+
+static inline cputime_t expires_to_cputime(unsigned long long expires)
+{
+	return (__force cputime_t)expires;
+}
 
 struct cpu_timer_list {
 	struct list_head entry;
-	union cpu_time_count expires, incr;
+	unsigned long long expires, incr;
 	struct task_struct *task;
 	int firing;
 };
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 42670e9..c3c4ea1 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -51,59 +51,28 @@ static int check_clock(const clockid_t which_clock)
 	return error;
 }
 
-static inline union cpu_time_count
+static inline unsigned long long
 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
 {
-	union cpu_time_count ret;
-	ret.sched = 0;		/* high half always zero when .cpu used */
+	unsigned long long ret;
+
+	ret = 0;		/* high half always zero when .cpu used */
 	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-		ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
+		ret = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
 	} else {
-		ret.cpu = timespec_to_cputime(tp);
+		ret = cputime_to_expires(timespec_to_cputime(tp));
 	}
 	return ret;
 }
 
 static void sample_to_timespec(const clockid_t which_clock,
-			       union cpu_time_count cpu,
+			       unsigned long long expires,
 			       struct timespec *tp)
 {
 	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
-		*tp = ns_to_timespec(cpu.sched);
+		*tp = ns_to_timespec(expires);
 	else
-		cputime_to_timespec(cpu.cpu, tp);
-}
-
-static inline int cpu_time_before(const clockid_t which_clock,
-				  union cpu_time_count now,
-				  union cpu_time_count then)
-{
-	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-		return now.sched < then.sched;
-	}  else {
-		return now.cpu < then.cpu;
-	}
-}
-static inline void cpu_time_add(const clockid_t which_clock,
-				union cpu_time_count *acc,
-			        union cpu_time_count val)
-{
-	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-		acc->sched += val.sched;
-	}  else {
-		acc->cpu += val.cpu;
-	}
-}
-static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
-						union cpu_time_count a,
-						union cpu_time_count b)
-{
-	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-		a.sched -= b.sched;
-	}  else {
-		a.cpu -= b.cpu;
-	}
-	return a;
+		cputime_to_timespec((__force cputime_t)expires, tp);
 }
 
 /*
@@ -111,47 +80,31 @@ static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
  * given the current clock sample.
  */
 static void bump_cpu_timer(struct k_itimer *timer,
-				  union cpu_time_count now)
+			   unsigned long long now)
 {
 	int i;
+	unsigned long long delta, incr;
 
-	if (timer->it.cpu.incr.sched == 0)
+	if (timer->it.cpu.incr == 0)
 		return;
 
-	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
-		unsigned long long delta, incr;
+	if (now < timer->it.cpu.expires)
+		return;
 
-		if (now.sched < timer->it.cpu.expires.sched)
-			return;
-		incr = timer->it.cpu.incr.sched;
-		delta = now.sched + incr - timer->it.cpu.expires.sched;
-		/* Don't use (incr*2 < delta), incr*2 might overflow. */
-		for (i = 0; incr < delta - incr; i++)
-			incr = incr << 1;
-		for (; i >= 0; incr >>= 1, i--) {
-			if (delta < incr)
-				continue;
-			timer->it.cpu.expires.sched += incr;
-			timer->it_overrun += 1 << i;
-			delta -= incr;
-		}
-	} else {
-		cputime_t delta, incr;
+	incr = timer->it.cpu.incr;
+	delta = now + incr - timer->it.cpu.expires;
 
-		if (now.cpu < timer->it.cpu.expires.cpu)
-			return;
-		incr = timer->it.cpu.incr.cpu;
-		delta = now.cpu + incr - timer->it.cpu.expires.cpu;
-		/* Don't use (incr*2 < delta), incr*2 might overflow. */
-		for (i = 0; incr < delta - incr; i++)
-			     incr += incr;
-		for (; i >= 0; incr = incr >> 1, i--) {
-			if (delta < incr)
-				continue;
-			timer->it.cpu.expires.cpu += incr;
-			timer->it_overrun += 1 << i;
-			delta -= incr;
-		}
+	/* Don't use (incr*2 < delta), incr*2 might overflow. */
+	for (i = 0; incr < delta - incr; i++)
+		incr = incr << 1;
+
+	for (; i >= 0; incr >>= 1, i--) {
+		if (delta < incr)
+			continue;
+
+		timer->it.cpu.expires += incr;
+		timer->it_overrun += 1 << i;
+		delta -= incr;
 	}
 }
 
@@ -170,21 +123,21 @@ static inline int task_cputime_zero(const struct task_cputime *cputime)
 	return 0;
 }
 
-static inline cputime_t prof_ticks(struct task_struct *p)
+static inline unsigned long long prof_ticks(struct task_struct *p)
 {
 	cputime_t utime, stime;
 
 	task_cputime(p, &utime, &stime);
 
-	return utime + stime;
+	return cputime_to_expires(utime + stime);
 }
-static inline cputime_t virt_ticks(struct task_struct *p)
+static inline unsigned long long virt_ticks(struct task_struct *p)
 {
 	cputime_t utime;
 
 	task_cputime(p, &utime, NULL);
 
-	return utime;
+	return cputime_to_expires(utime);
 }
 
 static int
@@ -225,19 +178,19 @@ posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
  * Sample a per-thread clock for the given task.
  */
 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
-			    union cpu_time_count *cpu)
+			    unsigned long long *sample)
 {
 	switch (CPUCLOCK_WHICH(which_clock)) {
 	default:
 		return -EINVAL;
 	case CPUCLOCK_PROF:
-		cpu->cpu = prof_ticks(p);
+		*sample = prof_ticks(p);
 		break;
 	case CPUCLOCK_VIRT:
-		cpu->cpu = virt_ticks(p);
+		*sample = virt_ticks(p);
 		break;
 	case CPUCLOCK_SCHED:
-		cpu->sched = task_sched_runtime(p);
+		*sample = task_sched_runtime(p);
 		break;
 	}
 	return 0;
@@ -284,7 +237,7 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
  */
 static int cpu_clock_sample_group(const clockid_t which_clock,
 				  struct task_struct *p,
-				  union cpu_time_count *cpu)
+				  unsigned long long *sample)
 {
 	struct task_cputime cputime;
 
@@ -293,15 +246,15 @@ static int cpu_clock_sample_group(const clockid_t which_clock,
 		return -EINVAL;
 	case CPUCLOCK_PROF:
 		thread_group_cputime(p, &cputime);
-		cpu->cpu = cputime.utime + cputime.stime;
+		*sample = cputime_to_expires(cputime.utime + cputime.stime);
 		break;
 	case CPUCLOCK_VIRT:
 		thread_group_cputime(p, &cputime);
-		cpu->cpu = cputime.utime;
+		*sample = cputime_to_expires(cputime.utime);
 		break;
 	case CPUCLOCK_SCHED:
 		thread_group_cputime(p, &cputime);
-		cpu->sched = cputime.sum_exec_runtime;
+		*sample = cputime.sum_exec_runtime;
 		break;
 	}
 	return 0;
@@ -312,7 +265,7 @@ static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 {
 	const pid_t pid = CPUCLOCK_PID(which_clock);
 	int error = -EINVAL;
-	union cpu_time_count rtn;
+	unsigned long long rtn;
 
 	if (pid == 0) {
 		/*
@@ -461,30 +414,30 @@ static void cleanup_timers(struct list_head *head,
 
 	list_for_each_entry_safe(timer, next, head, entry) {
 		list_del_init(&timer->entry);
-		if (timer->expires.cpu < ptime) {
-			timer->expires.cpu = 0;
+		if (timer->expires < cputime_to_expires(ptime)) {
+			timer->expires = 0;
 		} else {
-			timer->expires.cpu -= ptime;
+			timer->expires -= cputime_to_expires(ptime);
 		}
 	}
 
 	++head;
 	list_for_each_entry_safe(timer, next, head, entry) {
 		list_del_init(&timer->entry);
-		if (timer->expires.cpu < utime) {
-			timer->expires.cpu = 0;
+		if (timer->expires < cputime_to_expires(utime)) {
+			timer->expires = 0;
 		} else {
-			timer->expires.cpu -= utime;
+			timer->expires -= cputime_to_expires(utime);
 		}
 	}
 
 	++head;
 	list_for_each_entry_safe(timer, next, head, entry) {
 		list_del_init(&timer->entry);
-		if (timer->expires.sched < sum_exec_runtime) {
-			timer->expires.sched = 0;
+		if (timer->expires < sum_exec_runtime) {
+			timer->expires = 0;
 		} else {
-			timer->expires.sched -= sum_exec_runtime;
+			timer->expires -= sum_exec_runtime;
 		}
 	}
 }
@@ -516,7 +469,7 @@ void posix_cpu_timers_exit_group(struct task_struct *tsk)
 		       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 }
 
-static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
+static void clear_dead_task(struct k_itimer *timer, unsigned long long now)
 {
 	/*
 	 * That's all for this thread or process.
@@ -524,9 +477,7 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 	 */
 	put_task_struct(timer->it.cpu.task);
 	timer->it.cpu.task = NULL;
-	timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
-					     timer->it.cpu.expires,
-					     now);
+	timer->it.cpu.expires -= now;
 }
 
 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
@@ -558,14 +509,14 @@ static void arm_timer(struct k_itimer *timer)
 
 	listpos = head;
 	list_for_each_entry(next, head, entry) {
-		if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
+		if (nt->expires < next->expires)
 			break;
 		listpos = &next->entry;
 	}
 	list_add(&nt->entry, listpos);
 
 	if (listpos == head) {
-		union cpu_time_count *exp = &nt->expires;
+		unsigned long long exp = nt->expires;
 
 		/*
 		 * We are the new earliest-expiring POSIX 1.b timer, hence
@@ -576,17 +527,17 @@ static void arm_timer(struct k_itimer *timer)
 
 		switch (CPUCLOCK_WHICH(timer->it_clock)) {
 		case CPUCLOCK_PROF:
-			if (expires_gt(cputime_expires->prof_exp, exp->cpu))
-				cputime_expires->prof_exp = exp->cpu;
+			if (expires_gt(cputime_expires->prof_exp, expires_to_cputime(exp)))
+				cputime_expires->prof_exp = expires_to_cputime(exp);
 			break;
 		case CPUCLOCK_VIRT:
-			if (expires_gt(cputime_expires->virt_exp, exp->cpu))
-				cputime_expires->virt_exp = exp->cpu;
+			if (expires_gt(cputime_expires->virt_exp, expires_to_cputime(exp)))
+				cputime_expires->virt_exp = expires_to_cputime(exp);
 			break;
 		case CPUCLOCK_SCHED:
 			if (cputime_expires->sched_exp == 0 ||
-			    cputime_expires->sched_exp > exp->sched)
-				cputime_expires->sched_exp = exp->sched;
+			    cputime_expires->sched_exp > exp)
+				cputime_expires->sched_exp = exp;
 			break;
 		}
 	}
@@ -601,20 +552,20 @@ static void cpu_timer_fire(struct k_itimer *timer)
 		/*
 		 * User don't want any signal.
 		 */
-		timer->it.cpu.expires.sched = 0;
+		timer->it.cpu.expires = 0;
 	} else if (unlikely(timer->sigq == NULL)) {
 		/*
 		 * This a special case for clock_nanosleep,
 		 * not a normal timer from sys_timer_create.
 		 */
 		wake_up_process(timer->it_process);
-		timer->it.cpu.expires.sched = 0;
-	} else if (timer->it.cpu.incr.sched == 0) {
+		timer->it.cpu.expires = 0;
+	} else if (timer->it.cpu.incr == 0) {
 		/*
 		 * One-shot timer.  Clear it as soon as it's fired.
 		 */
 		posix_timer_event(timer, 0);
-		timer->it.cpu.expires.sched = 0;
+		timer->it.cpu.expires = 0;
 	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 		/*
 		 * The signal did not get queued because the signal
@@ -632,7 +583,7 @@ static void cpu_timer_fire(struct k_itimer *timer)
  */
 static int cpu_timer_sample_group(const clockid_t which_clock,
 				  struct task_struct *p,
-				  union cpu_time_count *cpu)
+				  unsigned long long *sample)
 {
 	struct task_cputime cputime;
 
@@ -641,13 +592,13 @@ static int cpu_timer_sample_group(const clockid_t which_clock,
 	default:
 		return -EINVAL;
 	case CPUCLOCK_PROF:
-		cpu->cpu = cputime.utime + cputime.stime;
+		*sample = cputime_to_expires(cputime.utime + cputime.stime);
 		break;
 	case CPUCLOCK_VIRT:
-		cpu->cpu = cputime.utime;
+		*sample = cputime_to_expires(cputime.utime);
 		break;
 	case CPUCLOCK_SCHED:
-		cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
+		*sample = cputime.sum_exec_runtime + task_delta_exec(p);
 		break;
 	}
 	return 0;
@@ -694,7 +645,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 			       struct itimerspec *new, struct itimerspec *old)
 {
 	struct task_struct *p = timer->it.cpu.task;
-	union cpu_time_count old_expires, new_expires, old_incr, val;
+	unsigned long long old_expires, new_expires, old_incr, val;
 	int ret;
 
 	if (unlikely(p == NULL)) {
@@ -749,7 +700,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 	}
 
 	if (old) {
-		if (old_expires.sched == 0) {
+		if (old_expires == 0) {
 			old->it_value.tv_sec = 0;
 			old->it_value.tv_nsec = 0;
 		} else {
@@ -764,11 +715,8 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 			 * new setting.
 			 */
 			bump_cpu_timer(timer, val);
-			if (cpu_time_before(timer->it_clock, val,
-					    timer->it.cpu.expires)) {
-				old_expires = cpu_time_sub(
-					timer->it_clock,
-					timer->it.cpu.expires, val);
+			if (val < timer->it.cpu.expires) {
+				old_expires = timer->it.cpu.expires - val;
 				sample_to_timespec(timer->it_clock,
 						   old_expires,
 						   &old->it_value);
@@ -791,8 +739,8 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 		goto out;
 	}
 
-	if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
-		cpu_time_add(timer->it_clock, &new_expires, val);
+	if (new_expires != 0 && !(flags & TIMER_ABSTIME)) {
+		new_expires += val;
 	}
 
 	/*
@@ -801,8 +749,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 	 * arm the timer (we'll just fake it for timer_gettime).
 	 */
 	timer->it.cpu.expires = new_expires;
-	if (new_expires.sched != 0 &&
-	    cpu_time_before(timer->it_clock, val, new_expires)) {
+	if (new_expires != 0 && val < new_expires) {
 		arm_timer(timer);
 	}
 
@@ -826,8 +773,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 	timer->it_overrun_last = 0;
 	timer->it_overrun = -1;
 
-	if (new_expires.sched != 0 &&
-	    !cpu_time_before(timer->it_clock, val, new_expires)) {
+	if (new_expires != 0 && !(val < new_expires)) {
 		/*
 		 * The designated time already passed, so we notify
 		 * immediately, even if the thread never runs to
@@ -849,7 +795,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 
 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 {
-	union cpu_time_count now;
+	unsigned long long now;
 	struct task_struct *p = timer->it.cpu.task;
 	int clear_dead;
 
@@ -859,7 +805,7 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 	sample_to_timespec(timer->it_clock,
 			   timer->it.cpu.incr, &itp->it_interval);
 
-	if (timer->it.cpu.expires.sched == 0) {	/* Timer not armed at all.  */
+	if (timer->it.cpu.expires == 0) {	/* Timer not armed at all.  */
 		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 		return;
 	}
@@ -891,7 +837,7 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 			 */
 			put_task_struct(p);
 			timer->it.cpu.task = NULL;
-			timer->it.cpu.expires.sched = 0;
+			timer->it.cpu.expires = 0;
 			read_unlock(&tasklist_lock);
 			goto dead;
 		} else {
@@ -912,10 +858,9 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 		goto dead;
 	}
 
-	if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
+	if (now < timer->it.cpu.expires) {
 		sample_to_timespec(timer->it_clock,
-				   cpu_time_sub(timer->it_clock,
-						timer->it.cpu.expires, now),
+				   timer->it.cpu.expires - now,
 				   &itp->it_value);
 	} else {
 		/*
@@ -946,8 +891,8 @@ static void check_thread_timers(struct task_struct *tsk,
 		struct cpu_timer_list *t = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || prof_ticks(tsk) < t->expires.cpu) {
-			tsk->cputime_expires.prof_exp = t->expires.cpu;
+		if (!--maxfire || prof_ticks(tsk) < t->expires) {
+			tsk->cputime_expires.prof_exp = expires_to_cputime(t->expires);
 			break;
 		}
 		t->firing = 1;
@@ -961,8 +906,8 @@ static void check_thread_timers(struct task_struct *tsk,
 		struct cpu_timer_list *t = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || virt_ticks(tsk) < t->expires.cpu) {
-			tsk->cputime_expires.virt_exp = t->expires.cpu;
+		if (!--maxfire || virt_ticks(tsk) < t->expires) {
+			tsk->cputime_expires.virt_exp = expires_to_cputime(t->expires);
 			break;
 		}
 		t->firing = 1;
@@ -976,8 +921,8 @@ static void check_thread_timers(struct task_struct *tsk,
 		struct cpu_timer_list *t = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
-			tsk->cputime_expires.sched_exp = t->expires.sched;
+		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires) {
+			tsk->cputime_expires.sched_exp = t->expires;
 			break;
 		}
 		t->firing = 1;
@@ -1030,7 +975,8 @@ static void stop_process_timers(struct signal_struct *sig)
 static u32 onecputick;
 
 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
-			     cputime_t *expires, cputime_t cur_time, int signo)
+			     unsigned long long *expires,
+			     unsigned long long cur_time, int signo)
 {
 	if (!it->expires)
 		return;
@@ -1068,7 +1014,7 @@ static void check_process_timers(struct task_struct *tsk,
 {
 	int maxfire;
 	struct signal_struct *const sig = tsk->signal;
-	cputime_t utime, ptime, virt_expires, prof_expires;
+	unsigned long long utime, ptime, virt_expires, prof_expires;
 	unsigned long long sum_sched_runtime, sched_expires;
 	struct list_head *timers = sig->cpu_timers;
 	struct task_cputime cputime;
@@ -1078,8 +1024,8 @@ static void check_process_timers(struct task_struct *tsk,
 	 * Collect the current process totals.
 	 */
 	thread_group_cputimer(tsk, &cputime);
-	utime = cputime.utime;
-	ptime = utime + cputime.stime;
+	utime = cputime_to_expires(cputime.utime);
+	ptime = utime + cputime_to_expires(cputime.stime);
 	sum_sched_runtime = cputime.sum_exec_runtime;
 	maxfire = 20;
 	prof_expires = 0;
@@ -1087,8 +1033,8 @@ static void check_process_timers(struct task_struct *tsk,
 		struct cpu_timer_list *tl = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || ptime < tl->expires.cpu) {
-			prof_expires = tl->expires.cpu;
+		if (!--maxfire || ptime < tl->expires) {
+			prof_expires = tl->expires;
 			break;
 		}
 		tl->firing = 1;
@@ -1102,8 +1048,8 @@ static void check_process_timers(struct task_struct *tsk,
 		struct cpu_timer_list *tl = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || utime < tl->expires.cpu) {
-			virt_expires = tl->expires.cpu;
+		if (!--maxfire || utime < tl->expires) {
+			virt_expires = tl->expires;
 			break;
 		}
 		tl->firing = 1;
@@ -1117,8 +1063,8 @@ static void check_process_timers(struct task_struct *tsk,
 		struct cpu_timer_list *tl = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
-			sched_expires = tl->expires.sched;
+		if (!--maxfire || sum_sched_runtime < tl->expires) {
+			sched_expires = tl->expires;
 			break;
 		}
 		tl->firing = 1;
@@ -1162,8 +1108,8 @@ static void check_process_timers(struct task_struct *tsk,
 		}
 	}
 
-	sig->cputime_expires.prof_exp = prof_expires;
-	sig->cputime_expires.virt_exp = virt_expires;
+	sig->cputime_expires.prof_exp = expires_to_cputime(prof_expires);
+	sig->cputime_expires.virt_exp = expires_to_cputime(virt_expires);
 	sig->cputime_expires.sched_exp = sched_expires;
 	if (task_cputime_zero(&sig->cputime_expires))
 		stop_process_timers(sig);
@@ -1176,7 +1122,7 @@ static void check_process_timers(struct task_struct *tsk,
 void posix_cpu_timer_schedule(struct k_itimer *timer)
 {
 	struct task_struct *p = timer->it.cpu.task;
-	union cpu_time_count now;
+	unsigned long long now;
 
 	if (unlikely(p == NULL))
 		/*
@@ -1205,7 +1151,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 			 */
 			put_task_struct(p);
 			timer->it.cpu.task = p = NULL;
-			timer->it.cpu.expires.sched = 0;
+			timer->it.cpu.expires = 0;
 			goto out_unlock;
 		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
 			/*
@@ -1387,7 +1333,7 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 			   cputime_t *newval, cputime_t *oldval)
 {
-	union cpu_time_count now;
+	unsigned long long now;
 
 	BUG_ON(clock_idx == CPUCLOCK_SCHED);
 	cpu_timer_sample_group(clock_idx, tsk, &now);
@@ -1399,17 +1345,17 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 		 * it to be absolute.
 		 */
 		if (*oldval) {
-			if (*oldval <= now.cpu) {
+			if (*oldval <= now) {
 				/* Just about to fire. */
 				*oldval = cputime_one_jiffy;
 			} else {
-				*oldval -= now.cpu;
+				*oldval -= now;
 			}
 		}
 
 		if (!*newval)
 			goto out;
-		*newval += now.cpu;
+		*newval += now;
 	}
 
 	/*
@@ -1459,7 +1405,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		}
 
 		while (!signal_pending(current)) {
-			if (timer.it.cpu.expires.sched == 0) {
+			if (timer.it.cpu.expires == 0) {
 				/*
 				 * Our timer fired and was reset, below
 				 * deletion can not fail.
-- 
1.7.5.4

[PATCH 2/7] posix_cpu_timers: consolidate timer list cleanups

[Frederic Weisbecker]

Cleaning up the posix cpu timers on task exit shares some common code
among timer list types, most notably the list traversal and expiry time
update.

Unify this in a common helper.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/posix-cpu-timers.c |   48 +++++++++++++++++---------------------------
 1 files changed, 19 insertions(+), 29 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index c3c4ea1..b1450ce 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -399,6 +399,21 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
 	return ret;
 }
 
+static void cleanup_timers_list(struct list_head *head,
+				unsigned long long curr)
+{
+	struct cpu_timer_list *timer, *next;
+
+	list_for_each_entry_safe(timer, next, head, entry) {
+		list_del_init(&timer->entry);
+		if (timer->expires < curr) {
+			timer->expires = 0;
+		} else {
+			timer->expires -= curr;
+		}
+	}
+}
+
 /*
  * Clean out CPU timers still ticking when a thread exited.  The task
  * pointer is cleared, and the expiry time is replaced with the residual
@@ -409,37 +424,12 @@ static void cleanup_timers(struct list_head *head,
 			   cputime_t utime, cputime_t stime,
 			   unsigned long long sum_exec_runtime)
 {
-	struct cpu_timer_list *timer, *next;
-	cputime_t ptime = utime + stime;
 
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (timer->expires < cputime_to_expires(ptime)) {
-			timer->expires = 0;
-		} else {
-			timer->expires -= cputime_to_expires(ptime);
-		}
-	}
-
-	++head;
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (timer->expires < cputime_to_expires(utime)) {
-			timer->expires = 0;
-		} else {
-			timer->expires -= cputime_to_expires(utime);
-		}
-	}
+	cputime_t ptime = utime + stime;
 
-	++head;
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (timer->expires < sum_exec_runtime) {
-			timer->expires = 0;
-		} else {
-			timer->expires -= sum_exec_runtime;
-		}
-	}
+	cleanup_timers_list(head, cputime_to_expires(ptime));
+	cleanup_timers_list(++head, cputime_to_expires(utime));
+	cleanup_timers_list(++head, sum_exec_runtime);
 }
 
 /*
-- 
1.7.5.4

[PATCH 3/7] posix_cpu_timers: consolidate expired timers check

[Frederic Weisbecker]

Consolidate the common code amongst per thread and per process timers list
on tick time.

List traversal, expiry check and subsequent updates can be shared in a
common helper.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/posix-cpu-timers.c |  118 +++++++++++++--------------------------------
 1 files changed, 33 insertions(+), 85 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index b1450ce..92a4fbf 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -862,6 +862,28 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 	}
 }
 
+static unsigned long long
+check_timers_list(struct list_head *timers,
+		  struct list_head *firing,
+		  unsigned long long curr)
+{
+	int maxfire = 20;
+
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *t;
+
+		t = list_first_entry(timers, struct cpu_timer_list, entry);
+
+		if (!--maxfire || curr < t->expires)
+			return t->expires;
+
+		t->firing = 1;
+		list_move_tail(&t->entry, firing);
+	}
+
+	return 0;
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them off
  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
@@ -870,54 +892,20 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 static void check_thread_timers(struct task_struct *tsk,
 				struct list_head *firing)
 {
-	int maxfire;
 	struct list_head *timers = tsk->cpu_timers;
 	struct signal_struct *const sig = tsk->signal;
+	struct task_cputime *tsk_expires = &tsk->cputime_expires;
+	unsigned long long expires;
 	unsigned long soft;
 
-	maxfire = 20;
-	tsk->cputime_expires.prof_exp = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || prof_ticks(tsk) < t->expires) {
-			tsk->cputime_expires.prof_exp = expires_to_cputime(t->expires);
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
+	expires = check_timers_list(timers, firing, prof_ticks(tsk));
+	tsk_expires->prof_exp = expires_to_cputime(expires);
 
-	++timers;
-	maxfire = 20;
-	tsk->cputime_expires.virt_exp = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || virt_ticks(tsk) < t->expires) {
-			tsk->cputime_expires.virt_exp = expires_to_cputime(t->expires);
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
+	expires = check_timers_list(++timers, firing, virt_ticks(tsk));
+	tsk_expires->virt_exp = expires_to_cputime(expires);
 
-	++timers;
-	maxfire = 20;
-	tsk->cputime_expires.sched_exp = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires) {
-			tsk->cputime_expires.sched_exp = t->expires;
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
+	tsk_expires->sched_exp = check_timers_list(++timers, firing,
+						   tsk->se.sum_exec_runtime);
 
 	/*
 	 * Check for the special case thread timers.
@@ -1002,7 +990,6 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 static void check_process_timers(struct task_struct *tsk,
 				 struct list_head *firing)
 {
-	int maxfire;
 	struct signal_struct *const sig = tsk->signal;
 	unsigned long long utime, ptime, virt_expires, prof_expires;
 	unsigned long long sum_sched_runtime, sched_expires;
@@ -1017,49 +1004,10 @@ static void check_process_timers(struct task_struct *tsk,
 	utime = cputime_to_expires(cputime.utime);
 	ptime = utime + cputime_to_expires(cputime.stime);
 	sum_sched_runtime = cputime.sum_exec_runtime;
-	maxfire = 20;
-	prof_expires = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || ptime < tl->expires) {
-			prof_expires = tl->expires;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
 
-	++timers;
-	maxfire = 20;
-	virt_expires = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || utime < tl->expires) {
-			virt_expires = tl->expires;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
-
-	++timers;
-	maxfire = 20;
-	sched_expires = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || sum_sched_runtime < tl->expires) {
-			sched_expires = tl->expires;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
+	prof_expires = check_timers_list(timers, firing, ptime);
+	virt_expires = check_timers_list(++timers, firing, utime);
+	sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);
 
 	/*
 	 * Check for the special case process timers.
-- 
1.7.5.4

[PATCH 4/7] selftests: add basic posix timers selftests

[Frederic Weisbecker]

Add some initial basic tests on a few posix timers interface such as
setitimer() and timer_settime().

These simply check that expiration happens in a reasonable timeframe after
expected elapsed clock time (user time, user + system time, real time,
...).

This is helpful for finding basic breakages while hacking
on this subsystem.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 tools/testing/selftests/Makefile              |    1 +
 tools/testing/selftests/timers/Makefile       |    8 +
 tools/testing/selftests/timers/posix_timers.c |  221 +++++++++++++++++++++++++
 3 files changed, 230 insertions(+), 0 deletions(-)
 create mode 100644 tools/testing/selftests/timers/Makefile
 create mode 100644 tools/testing/selftests/timers/posix_timers.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 0a63658..4cb14ca 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -6,6 +6,7 @@ TARGETS += memory-hotplug
 TARGETS += mqueue
 TARGETS += net
 TARGETS += ptrace
+TARGETS += timers
 TARGETS += vm
 
 all:
diff --git a/tools/testing/selftests/timers/Makefile b/tools/testing/selftests/timers/Makefile
new file mode 100644
index 0000000..eb2859f
--- /dev/null
+++ b/tools/testing/selftests/timers/Makefile
@@ -0,0 +1,8 @@
+all:
+	gcc posix_timers.c -o posix_timers -lrt
+
+run_tests: all
+	./posix_timers
+
+clean:
+	rm -f ./posix_timers
diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
new file mode 100644
index 0000000..4fa655d
--- /dev/null
+++ b/tools/testing/selftests/timers/posix_timers.c
@@ -0,0 +1,221 @@
+/*
+ * Copyright (C) 2013 Red Hat, Inc., Frederic Weisbecker <fweisbec@redhat.com>
+ *
+ * Licensed under the terms of the GNU GPL License version 2
+ *
+ * Selftests for a few posix timers interface.
+ *
+ * Kernel loop code stolen from Steven Rostedt <srostedt@redhat.com>
+ */
+
+#include <sys/time.h>
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+#include <time.h>
+#include <pthread.h>
+
+#define DELAY 2
+#define USECS_PER_SEC 1000000
+
+static volatile int done;
+
+/* Busy loop in userspace to elapse ITIMER_VIRTUAL */
+static void user_loop(void)
+{
+	while (!done);
+}
+
+/*
+ * Try to spend as much time as possible in kernelspace
+ * to elapse ITIMER_PROF.
+ */
+static void kernel_loop(void)
+{
+	void *addr = sbrk(0);
+
+	while (!done) {
+		brk(addr + 4096);
+		brk(addr);
+	}
+}
+
+/*
+ * Sleep until ITIMER_REAL expiration.
+ */
+static void idle_loop(void)
+{
+	pause();
+}
+
+static void sig_handler(int nr)
+{
+	done = 1;
+}
+
+/*
+ * Check the expected timer expiration matches the GTOD elapsed delta since
+ * we armed the timer. Keep a 0.5 sec error margin due to various jitter.
+ */
+static int check_diff(struct timeval start, struct timeval end)
+{
+	long long diff;
+
+	diff = end.tv_usec - start.tv_usec;
+	diff += (end.tv_sec - start.tv_sec) * USECS_PER_SEC;
+
+	if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
+		printf("Diff too high: %lld..", diff);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int check_itimer(int which)
+{
+	int err;
+	struct timeval start, end;
+	struct itimerval val = {
+		.it_value.tv_sec = DELAY,
+	};
+
+	printf("Check itimer ");
+
+	if (which == ITIMER_VIRTUAL)
+		printf("virtual... ");
+	else if (which == ITIMER_PROF)
+		printf("prof... ");
+	else if (which == ITIMER_REAL)
+		printf("real... ");
+
+	fflush(stdout);
+
+	done = 0;
+
+	if (which == ITIMER_VIRTUAL)
+		signal(SIGVTALRM, sig_handler);
+	else if (which == ITIMER_PROF)
+		signal(SIGPROF, sig_handler);
+	else if (which == ITIMER_REAL)
+		signal(SIGALRM, sig_handler);
+
+	err = gettimeofday(&start, NULL);
+	if (err < 0) {
+		perror("Can't call gettimeofday()\n");
+		return -1;
+	}
+
+	err = setitimer(which, &val, NULL);
+	if (err < 0) {
+		perror("Can't set timer\n");
+		return -1;
+	}
+
+	if (which == ITIMER_VIRTUAL)
+		user_loop();
+	else if (which == ITIMER_PROF)
+		kernel_loop();
+	else if (which == ITIMER_REAL)
+		idle_loop();
+
+	gettimeofday(&end, NULL);
+	if (err < 0) {
+		perror("Can't call gettimeofday()\n");
+		return -1;
+	}
+
+	if (!check_diff(start, end))
+		printf("[OK]\n");
+	else
+		printf("[FAIL]\n");
+
+	return 0;
+}
+
+static int check_timer_create(int which)
+{
+	int err;
+	timer_t id;
+	struct timeval start, end;
+	struct itimerspec val = {
+		.it_value.tv_sec = DELAY,
+	};
+
+	printf("Check timer_create() ");
+	if (which == CLOCK_THREAD_CPUTIME_ID) {
+		printf("per thread... ");
+	} else if (which == CLOCK_PROCESS_CPUTIME_ID) {
+		printf("per process... ");
+	}
+	fflush(stdout);
+
+	done = 0;
+	timer_create(which, NULL, &id);
+	if (err < 0) {
+		perror("Can't create timer\n");
+		return -1;
+	}
+	signal(SIGALRM, sig_handler);
+
+	err = gettimeofday(&start, NULL);
+	if (err < 0) {
+		perror("Can't call gettimeofday()\n");
+		return -1;
+	}
+
+	err = timer_settime(id, 0, &val, NULL);
+	if (err < 0) {
+		perror("Can't set timer\n");
+		return -1;
+	}
+
+	user_loop();
+
+	gettimeofday(&end, NULL);
+	if (err < 0) {
+		perror("Can't call gettimeofday()\n");
+		return -1;
+	}
+
+	if (!check_diff(start, end))
+		printf("[OK]\n");
+	else
+		printf("[FAIL]\n");
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int err;
+
+	printf("Testing posix timers. False negative may happen on CPU execution \n");
+	printf("based timers if other threads run on the CPU...\n");
+
+	if (check_itimer(ITIMER_VIRTUAL) < 0)
+		return -1;
+
+	if (check_itimer(ITIMER_PROF) < 0)
+		return -1;
+
+	if (check_itimer(ITIMER_REAL) < 0)
+		return -1;
+
+	if (check_timer_create(CLOCK_THREAD_CPUTIME_ID) < 0)
+		return -1;
+
+	/*
+	 * It's unfortunately hard to reliably test a timer expiration
+	 * on parallel multithread cputime. We could arm it to expire
+	 * on DELAY * nr_threads, with nr_threads busy looping, then wait
+	 * the normal DELAY since the time is elapsing nr_threads faster.
+	 * But for that we need to ensure we have real physical free CPUs
+	 * to ensure true parallelism. So test only one thread until we
+	 * find a better solution.
+	 */
+	if (check_timer_create(CLOCK_PROCESS_CPUTIME_ID) < 0)
+		return -1;
+
+	return 0;
+}
-- 
1.7.5.4

[PATCH 5/7] posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()

[Frederic Weisbecker]

In order to re-arm a timer after it fired, we take a sample of the current
process or thread cputime.

If the task is dying though, we don't arm anything but we cache the
remaining timer expiration delta for further reads.

Something similar is performed in posix_cpu_timer_get() but here we forget
to take the process wide cputime sample before caching it.

As a result we are storing random stack content, leading every further
reads of that timer to return junk values.

Fix this by taking the appropriate sample in the case of process wide
timers.

This probably doesn't matter much in practice because, at this stage, the
thread is the last one in the group and we reached exit_notify().  This
implies that we called exit_itimers() and there should be no more timers
to handle for that task.

So this is likely dead code anyway but let's fix the current logic
and the warning that came along:

    kernel/posix-cpu-timers.c: In function 'posix_cpu_timer_schedule':
    kernel/posix-cpu-timers.c:1127: warning: 'now' may be used uninitialized in this function

Then we can start to think further about cleaning up that code.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Chen Gang <gang.chen@asianux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/posix-cpu-timers.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 92a4fbf..4ebd8ad 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1097,6 +1097,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 			 * not yet reaped.  Take this opportunity to
 			 * drop our task ref.
 			 */
+			cpu_timer_sample_group(timer->it_clock, p, &now);
 			clear_dead_task(timer, now);
 			goto out_unlock;
 		}
-- 
1.7.5.4

[PATCH 6/7] posix_timers: fix racy timer delta caching on task exit

[Frederic Weisbecker]

When a task exits, we perform a caching of the remaining cputime delta
before expiring of its timers.

This is done from the following places:

* When the task is reaped. We iterate through its list of
  posix cpu timers and store the remaining timer delta to
  the timer struct instead of the absolute value.
  (See posix_cpu_timers_exit() / posix_cpu_timers_exit_group() )

* When we call posix_cpu_timer_get() or posix_cpu_timer_schedule().
  If the timer's task is considered dying when watched from these
  places, the same conversion from absolute to relative expiry time
  is performed. Then the given task's reference is released.
  (See clear_dead_task() ).

The relevance of this caching is questionable but this is another
and deeper debate.

The big issue here is that these two sources of caching don't mix
up very well together.

More specifically, the caching can easily be done twice, resulting
in a wrong delta as it gets spuriously substracted a second time by
the elapsed clock. This can happen in the following scenario:

1) The task exits and gets reaped: we call posix_cpu_timers_exit()
   and the absolute timer expiry values are converted to a relative
   delta.

2) timer_gettime() -> posix_cpu_timer_get() is called and relies on
   clear_dead_task() because  tsk->exit_state == EXIT_DEAD.
   The delta gets substracted again by the elapsed clock and we return
   a wrong result.

To fix this, just remove the caching done on task reaping time.  It
doesn't bring much value on its own.  The caching done from
posix_cpu_timer_get/schedule is enough.

And it would also be hard to get it really right: we could make it put and
clear the target task in the timer struct so that readers know if they are
dealing with a relative cached of absolute value.  But it would be racy.
The only safe way to do it would be to lock the itimer->it_lock so that we
know nobody reads the cputime expiry value while we modify it and its
target task reference.  Doing so would involve some funny workarounds to
avoid circular lock against the sighand lock.  There is just no reason to
maintain this.

The user visible effect of this patch can be observed by running the
following code: it creates a subthread that launches a posix cputimer
which expires after 10 seconds. But then the subthread only busy loops for 2
seconds and exits. The parent reaps the subthread and read the timer value.
Its expected value should the be the initial timer's expiration value
minus the cputime elapsed in the subthread. Roughly 10 - 2 = 8 seconds:

	#include <sys/time.h>
	#include <stdio.h>
	#include <unistd.h>
	#include <time.h>
	#include <pthread.h>

	static timer_t id;
	static struct itimerspec val = { .it_value.tv_sec = 10, }, new;

	static void *thread(void *unused)
	{
		int err;
		struct timeval start, end, diff;

		timer_create(CLOCK_THREAD_CPUTIME_ID, NULL, &id);
		if (err < 0) {
			perror("Can't create timer\n");
			return NULL;
		}

		/* Arm 10 sec timer */
		err = timer_settime(id, 0, &val, NULL);
		if (err < 0) {
			perror("Can't set timer\n");
			return NULL;
		}

		/* Exit after 2 seconds of execution */
		gettimeofday(&start, NULL);
	        do {
			gettimeofday(&end, NULL);
			timersub(&end, &start, &diff);
		} while (diff.tv_sec < 2);

		return NULL;
	}

	int main(int argc, char **argv)
	{
		pthread_t pthread;
		int err;

		err = pthread_create(&pthread, NULL, thread, NULL);
		if (err) {
			perror("Can't create thread\n");
			return -1;
		}
		pthread_join(pthread, NULL);
		/* Just wait a little bit to make sure the child got reaped */
		sleep(1);
		err = timer_gettime(id, &new);
		if (err)
			perror("Can't get timer value\n");
		printf("%d %ld\n", new.it_value.tv_sec, new.it_value.tv_nsec);

		return 0;
	}

Before the patch:

       $ ./posix_cpu_timers
       6 2278074

After the patch:

      $ ./posix_cpu_timers
      8 1158766

Before the patch, the elapsed time got two more seconds spuriously accounted.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/posix-cpu-timers.c |   22 +++++++++++-----------
 1 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 4ebd8ad..c7f31aa 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -404,14 +404,8 @@ static void cleanup_timers_list(struct list_head *head,
 {
 	struct cpu_timer_list *timer, *next;
 
-	list_for_each_entry_safe(timer, next, head, entry) {
+	list_for_each_entry_safe(timer, next, head, entry)
 		list_del_init(&timer->entry);
-		if (timer->expires < curr) {
-			timer->expires = 0;
-		} else {
-			timer->expires -= curr;
-		}
-	}
 }
 
 /*
@@ -459,15 +453,21 @@ void posix_cpu_timers_exit_group(struct task_struct *tsk)
 		       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 }
 
-static void clear_dead_task(struct k_itimer *timer, unsigned long long now)
+static void clear_dead_task(struct k_itimer *itimer, unsigned long long now)
 {
+	struct cpu_timer_list *timer = &itimer->it.cpu;
+
 	/*
 	 * That's all for this thread or process.
 	 * We leave our residual in expires to be reported.
 	 */
-	put_task_struct(timer->it.cpu.task);
-	timer->it.cpu.task = NULL;
-	timer->it.cpu.expires -= now;
+	put_task_struct(timer->task);
+	timer->task = NULL;
+	if (timer->expires < now) {
+		timer->expires = 0;
+	} else {
+		timer->expires -= now;
+	}
 }
 
 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
-- 
1.7.5.4

[PATCH 7/7] posix-cpu-timers: don't account cpu timer after stopped thread runtime accounting

[Frederic Weisbecker]

From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

When tsk->signal->cputimer->running is 1, signal->cputimer (i.e. per process
timer account) and tsk->sum_sched_runtime (i.e. per thread timer account)
increase at the same pace because update_curr() increases both accounting.

However, there is one exception. When thread exiting, __exit_signal() turns
over task's sum_shced_runtime to sig->sum_sched_runtime, but it doesn't stop
signal->cputimer accounting.

This inconsistency makes POSIX timer wake up too early. This patch fixes it.

Original-patch-by: Olivier Langlois <olivier@trillion01.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/sched/stats.h |   39 ++++++++++++++++++++++++++++++++++++---
 1 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 2ef90a5..71bac97 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -162,6 +162,39 @@ sched_info_switch(struct task_struct *prev, struct task_struct *next)
  */
 
 /**
+ * cputimer_running - return true if cputimer is running
+ *
+ * @tsk:	Pointer to target task.
+ */
+static inline bool cputimer_running(struct task_struct *tsk)
+
+{
+	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+
+	if (!cputimer->running)
+		return false;
+
+	/*
+	 * After we flush the task's sum_exec_runtime to sig->sum_sched_runtime
+	 * in __exit_signal(), we won't account to the signal struct further
+	 * cputime consumed by that task, even though the task can still be
+	 * ticking after __exit_signal().
+	 *
+	 * In order to keep a consistent behaviour between thread group cputime
+	 * and thread group cputimer accounting, lets also ignore the cputime
+	 * elapsing after __exit_signal() in any thread group timer running.
+	 *
+	 * This makes sure that POSIX CPU clocks and timers are synchronized, so
+	 * that a POSIX CPU timer won't expire while the corresponding POSIX CPU
+	 * clock delta is behind the expiring timer value.
+	 */
+	if (unlikely(!tsk->sighand))
+		return false;
+
+	return true;
+}
+
+/**
  * account_group_user_time - Maintain utime for a thread group.
  *
  * @tsk:	Pointer to task structure.
@@ -176,7 +209,7 @@ static inline void account_group_user_time(struct task_struct *tsk,
 {
 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-	if (!cputimer->running)
+	if (!cputimer_running(tsk))
 		return;
 
 	raw_spin_lock(&cputimer->lock);
@@ -199,7 +232,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
 {
 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-	if (!cputimer->running)
+	if (!cputimer_running(tsk))
 		return;
 
 	raw_spin_lock(&cputimer->lock);
@@ -222,7 +255,7 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
 {
 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-	if (!cputimer->running)
+	if (!cputimer_running(tsk))
 		return;
 
 	raw_spin_lock(&cputimer->lock);
-- 
1.7.5.4