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timers: fix TIMER_ABSTIME for process wide cpu timers 

The POSIX timer interface allows for absolute time expiry values through the
TIMER_ABSTIME flag, therefore we have to synchronize the timer to the clock
every time we start it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-02-11 11:30:27 +01:00 committed by Ingo Molnar
parent 3fccfd67df
commit 4da94d49b2
2 changed files with 35 additions and 12 deletions
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13
include/linux/sched.h
View File

@ -2201,18 +2201,7 @@ static inline int spin_needbreak(spinlock_t *lock)
* Thread group CPU time accounting.
*/
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
static inline
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
unsigned long flags;
spin_lock_irqsave(&cputimer->lock, flags);
cputimer->running = 1;
*times = cputimer->cputime;
spin_unlock_irqrestore(&cputimer->lock, flags);
}
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times);
static inline void thread_group_cputime_init(struct signal_struct *sig)
{

34
kernel/posix-cpu-timers.c
View File

@ -261,6 +261,40 @@ out:
rcu_read_unlock();
}
static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
{
if (cputime_gt(b->utime, a->utime))
a->utime = b->utime;
if (cputime_gt(b->stime, a->stime))
a->stime = b->stime;
if (b->sum_exec_runtime > a->sum_exec_runtime)
a->sum_exec_runtime = b->sum_exec_runtime;
}
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct task_cputime sum;
unsigned long flags;
spin_lock_irqsave(&cputimer->lock, flags);
if (!cputimer->running) {
cputimer->running = 1;
/*
* The POSIX timer interface allows for absolute time expiry
* values through the TIMER_ABSTIME flag, therefore we have
* to synchronize the timer to the clock every time we start
* it.
*/
thread_group_cputime(tsk, &sum);
update_gt_cputime(&cputimer->cputime, &sum);
}
*times = cputimer->cputime;
spin_unlock_irqrestore(&cputimer->lock, flags);
}
/*
* Sample a process (thread group) clock for the given group_leader task.
* Must be called with tasklist_lock held for reading.