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posix-cpu-timers: Provide quick sample function for itimer 

get_itimer() needs a sample of the current thread group cputime. It invokes
thread_group_cputimer() - which is a misnomer. That function also starts
eventually the group cputime accouting which is bogus because the
accounting is already active when a timer is armed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192919.599658199@linutronix.de
This commit is contained in:
Thomas Gleixner 2019-08-21 21:08:51 +02:00
parent e5a8b65b4c
commit 19298fbf45
2 changed files with 22 additions and 1 deletions
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2
include/linux/sched/cputime.h
View File

@ -62,7 +62,7 @@ extern void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
*/
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times);
void thread_group_sample_cputime(struct task_struct *tsk, struct task_cputime *times);
/*
* The following are functions that support scheduler-internal time accounting.

21
kernel/time/posix-cpu-timers.c
View File

@ -232,6 +232,27 @@ static inline void sample_cputime_atomic(struct task_cputime *times,
times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
}
/**
* thread_group_sample_cputime - Sample cputime for a given task
* @tsk: Task for which cputime needs to be started
* @iimes: Storage for time samples
*
* Called from sys_getitimer() to calculate the expiry time of an active
* timer. That means group cputime accounting is already active. Called
* with task sighand lock held.
*
* Updates @times with an uptodate sample of the thread group cputimes.
*/
void thread_group_sample_cputime(struct task_struct *tsk,
struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
WARN_ON_ONCE(!cputimer->running);
sample_cputime_atomic(times, &cputimer->cputime_atomic);
}
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;