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Commit 6301cb95 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

sched: fix nr_uninterruptible accounting of frozen tasks really 



commit e3c8ca83 (sched: do not count frozen tasks toward load) broke
the nr_uninterruptible accounting on freeze/thaw. On freeze the task
is excluded from accounting with a check for (task->flags &
PF_FROZEN), but that flag is cleared before the task is thawed. So
while we prevent that the task with state TASK_UNINTERRUPTIBLE
is accounted to nr_uninterruptible on freeze we decrement
nr_uninterruptible on thaw.

Use a separate flag which is handled by the freezing task itself. Set
it before calling the scheduler with TASK_UNINTERRUPTIBLE state and
clear it after we return from frozen state.

Cc: <stable@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent a468d389

include/linux/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -209,7 +209,7 @@ extern unsigned long long time_sync_thresh; 
			((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)

#define task_contributes_to_load(task)	\

				((task->state & TASK_UNINTERRUPTIBLE) != 0 && \

				 (task->flags & PF_FROZEN) == 0)

				 (task->flags & PF_FREEZING) == 0)



#define __set_task_state(tsk, state_value)		\

	do { (tsk)->state = (state_value); } while (0)
@@ -1680,6 +1680,7 @@ extern cputime_t task_gtime(struct task_struct *p); 
#define PF_MEMALLOC	0x00000800	/* Allocating memory */

#define PF_FLUSHER	0x00001000	/* responsible for disk writeback */

#define PF_USED_MATH	0x00002000	/* if unset the fpu must be initialized before use */

#define PF_FREEZING	0x00004000	/* freeze in progress. do not account to load */

#define PF_NOFREEZE	0x00008000	/* this thread should not be frozen */

#define PF_FROZEN	0x00010000	/* frozen for system suspend */

#define PF_FSTRANS	0x00020000	/* inside a filesystem transaction */

kernel/freezer.c

+7 −0
Original line number Diff line number Diff line
@@ -44,12 +44,19 @@ void refrigerator(void) 
	recalc_sigpending(); /* We sent fake signal, clean it up */

	spin_unlock_irq(&current->sighand->siglock);



	/* prevent accounting of that task to load */

	current->flags |= PF_FREEZING;



	for (;;) {

		set_current_state(TASK_UNINTERRUPTIBLE);

		if (!frozen(current))

			break;

		schedule();

	}



	/* Remove the accounting blocker */

	current->flags &= ~PF_FREEZING;



	pr_debug("%s left refrigerator\n", current->comm);

	__set_current_state(save);

}