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Date: Tue, 17 Mar 2009 15:13:07 +0900
From: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To: linux-kernel@...r.kernel.org
CC: stable@...nel.org
Subject: [PATCH] posixtimers: Fix posix clock monotonicity
This patch rehires task_sched_runtime() and thread_group_sched_runtime()
which were removed at the time of 2.6.28-rc1.
These functions protect the sampling of clock with rq lock.
This rq lock is required not to update rq->clock during the sampling.
i.e. You may get ((banked runtime before update)+(delta after update)).
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc: stable@...nel.org [2.6.28.x]
---
kernel/posix-cpu-timers.c | 7 +++--
kernel/sched.c | 58 +++++++++++++++++++++++++++++++++++++++-----
2 files changed, 55 insertions(+), 10 deletions(-)
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 4e5288a..a65641a 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -294,7 +294,7 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
cpu->cpu = virt_ticks(p);
break;
case CPUCLOCK_SCHED:
- cpu->sched = p->se.sum_exec_runtime + task_delta_exec(p);
+ cpu->sched = task_sched_runtime(p);
break;
}
return 0;
@@ -310,18 +310,19 @@ static int cpu_clock_sample_group(const clockid_t which_clock,
{
struct task_cputime cputime;
- thread_group_cputime(p, &cputime);
switch (CPUCLOCK_WHICH(which_clock)) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
+ thread_group_cputime(p, &cputime);
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
+ thread_group_cputime(p, &cputime);
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
- cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
+ cpu->sched = thread_group_sched_runtime(p);
break;
}
return 0;
diff --git a/kernel/sched.c b/kernel/sched.c
index db66874..617d1b8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4066,7 +4066,23 @@ EXPORT_PER_CPU_SYMBOL(kstat);
/*
* Return any ns on the sched_clock that have not yet been banked in
* @p in case that task is currently running.
+ *
+ * Called with task_rq_lock() held on @rq.
*/
+static u64 __task_delta_exec(struct task_struct *p, struct rq *rq)
+{
+ u64 ns = 0;
+
+ if (task_current(rq, p)) {
+ update_rq_clock(rq);
+ ns = rq->clock - p->se.exec_start;
+ if ((s64)ns < 0)
+ ns = 0;
+ }
+
+ return ns;
+}
+
unsigned long long task_delta_exec(struct task_struct *p)
{
unsigned long flags;
@@ -4074,16 +4090,44 @@ unsigned long long task_delta_exec(struct task_struct *p)
u64 ns = 0;
rq = task_rq_lock(p, &flags);
+ ns = __task_delta_exec(p, rq);
+ task_rq_unlock(rq, &flags);
- if (task_current(rq, p)) {
- u64 delta_exec;
+ return ns;
+}
- update_rq_clock(rq);
- delta_exec = rq->clock - p->se.exec_start;
- if ((s64)delta_exec > 0)
- ns = delta_exec;
- }
+/*
+ * Return p->sum_exec_runtime plus any more ns on the sched_clock
+ * that have not yet been banked in case the task is currently running.
+ */
+unsigned long long task_sched_runtime(struct task_struct *p)
+{
+ unsigned long flags;
+ struct rq *rq;
+ u64 ns = 0;
+
+ rq = task_rq_lock(p, &flags);
+ ns = p->se.sum_exec_runtime + __task_delta_exec(p, rq);
+ task_rq_unlock(rq, &flags);
+
+ return ns;
+}
+/*
+ * Return sum_exec_runtime for the thread group plus any more ns on the
+ * sched_clock that have not yet been banked in case the task is currently
+ * running.
+ */
+unsigned long long thread_group_sched_runtime(struct task_struct *p)
+{
+ struct task_cputime totals;
+ unsigned long flags;
+ struct rq *rq;
+ u64 ns;
+
+ rq = task_rq_lock(p, &flags);
+ thread_group_cputime(p, &totals);
+ ns = totals.sum_exec_runtime + __task_delta_exec(p, rq);
task_rq_unlock(rq, &flags);
return ns;
--
1.6.2.1
--
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