Commit e4779015 authored by SeongJae Park's avatar SeongJae Park Committed by Linus Torvalds
Browse files

timers: implement usleep_idle_range() 

Patch series "mm/damon: Fix fake /proc/loadavg reports", v3.

This patchset fixes DAMON's fake load report issue.  The first patch
makes yet another variant of usleep_range() for this fix, and the second
patch fixes the issue of DAMON by making it using the newly introduced
function.

This patch (of 2):

Some kernel threads such as DAMON could need to repeatedly sleep in
micro seconds level.  Because usleep_range() sleeps in uninterruptible
state, however, such threads would make /proc/loadavg reports fake load.

To help such cases, this commit implements a variant of usleep_range()
called usleep_idle_range().  It is same to usleep_range() but sets the
state of the current task as TASK_IDLE while sleeping.

Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0c941cf3

include/linux/delay.h

+13 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
 */



#include <linux/math.h>

#include <linux/sched.h>



extern unsigned long loops_per_jiffy;
@@ -58,7 +59,18 @@ void calibrate_delay(void); 
void __attribute__((weak)) calibration_delay_done(void);

void msleep(unsigned int msecs);

unsigned long msleep_interruptible(unsigned int msecs);

void usleep_range(unsigned long min, unsigned long max);

void usleep_range_state(unsigned long min, unsigned long max,

			unsigned int state);



static inline void usleep_range(unsigned long min, unsigned long max)

{

	usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);

}



static inline void usleep_idle_range(unsigned long min, unsigned long max)

{

	usleep_range_state(min, max, TASK_IDLE);

}



static inline void ssleep(unsigned int seconds)

{

kernel/time/timer.c

+9 −7
Original line number Diff line number Diff line
@@ -2054,26 +2054,28 @@ unsigned long msleep_interruptible(unsigned int msecs) 
EXPORT_SYMBOL(msleep_interruptible);



/**

 * usleep_range - Sleep for an approximate time

 * usleep_range_state - Sleep for an approximate time in a given state

 * @min:	Minimum time in usecs to sleep

 * @max:	Maximum time in usecs to sleep

 * @state:	State of the current task that will be while sleeping

 *

 * In non-atomic context where the exact wakeup time is flexible, use

 * usleep_range() instead of udelay().  The sleep improves responsiveness

 * usleep_range_state() instead of udelay().  The sleep improves responsiveness

 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces

 * power usage by allowing hrtimers to take advantage of an already-

 * scheduled interrupt instead of scheduling a new one just for this sleep.

 */

void __sched usleep_range(unsigned long min, unsigned long max)

void __sched usleep_range_state(unsigned long min, unsigned long max,

				unsigned int state)

{

	ktime_t exp = ktime_add_us(ktime_get(), min);

	u64 delta = (u64)(max - min) * NSEC_PER_USEC;



	for (;;) {

		__set_current_state(TASK_UNINTERRUPTIBLE);

		__set_current_state(state);

		/* Do not return before the requested sleep time has elapsed */

		if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))

			break;

	}

}

EXPORT_SYMBOL(usleep_range);
 
EXPORT_SYMBOL(usleep_range_state);