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Commit 555347f6 authored by Frederic Weisbecker's avatar Frederic Weisbecker
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posix_timers: New API to prevent from stopping the tick when timers are running 



Bring a new helper that the full dynticks infrastructure can
call in order to know if it can safely stop the tick from
the posix cpu timers subsystem point of view.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
parent a8572160

include/linux/posix-timers.h

+2 −0
Original line number Diff line number Diff line
@@ -122,6 +122,8 @@ void run_posix_cpu_timers(struct task_struct *task); 
void posix_cpu_timers_exit(struct task_struct *task);

void posix_cpu_timers_exit_group(struct task_struct *task);



bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk);



void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx,

			   cputime_t *newval, cputime_t *oldval);

kernel/posix-cpu-timers.c

+26 −15
Original line number Diff line number Diff line
@@ -155,6 +155,21 @@ static void bump_cpu_timer(struct k_itimer *timer, 
	}

}



/**

 * task_cputime_zero - Check a task_cputime struct for all zero fields.

 *

 * @cputime:	The struct to compare.

 *

 * Checks @cputime to see if all fields are zero.  Returns true if all fields

 * are zero, false if any field is nonzero.

 */

static inline int task_cputime_zero(const struct task_cputime *cputime)

{

	if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)

		return 1;

	return 0;

}



static inline cputime_t prof_ticks(struct task_struct *p)

{

	cputime_t utime, stime;
@@ -654,6 +669,17 @@ static void posix_cpu_timer_kick_nohz(void) 
{

	schedule_work(&nohz_kick_work);

}



bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)

{

	if (!task_cputime_zero(&tsk->cputime_expires))

		return true;



	if (tsk->signal->cputimer.running)

		return true;



	return false;

}

#else

static inline void posix_cpu_timer_kick_nohz(void) { }

#endif
@@ -1032,21 +1058,6 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it, 
	}

}



/**

 * task_cputime_zero - Check a task_cputime struct for all zero fields.

 *

 * @cputime:	The struct to compare.

 *

 * Checks @cputime to see if all fields are zero.  Returns true if all fields

 * are zero, false if any field is nonzero.

 */

static inline int task_cputime_zero(const struct task_cputime *cputime)

{

	if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)

		return 1;

	return 0;

}



/*

 * Check for any per-thread CPU timers that have fired and move them

 * off the tsk->*_timers list onto the firing list.  Per-thread timers