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Commit 85f1d476 authored by Tejun Heo's avatar Tejun Heo
Browse files

freezer: test freezable conditions while holding freezer_lock 



try_to_freeze_tasks() and thaw_processes() use freezable() and
frozen() as preliminary tests before initiating operations on a task.
These are done without any synchronization and hinder with
synchronization cleanup without any real performance benefits.

In try_to_freeze_tasks(), open code self test and move PF_NOFREEZE and
frozen() tests inside freezer_lock in freeze_task().

thaw_processes() can simply drop freezable() test as frozen() test in
__thaw_task() is enough.

Note: This used to be a part of larger patch to fix set_freezable()
      race.  Separated out to satisfy ordering among dependent fixes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
parent 6907483b

kernel/freezer.c

+2 −1
Original line number Diff line number Diff line
@@ -109,7 +109,8 @@ bool freeze_task(struct task_struct *p, bool sig_only) 


	spin_lock_irqsave(&freezer_lock, flags);



	if (sig_only && !should_send_signal(p))

	if ((p->flags & PF_NOFREEZE) ||

	    (sig_only && !should_send_signal(p)))

		goto out_unlock;



	if (frozen(p))

kernel/power/process.c

+1 −15
Original line number Diff line number Diff line
@@ -22,14 +22,6 @@ 
 */

#define TIMEOUT	(20 * HZ)



static inline int freezable(struct task_struct * p)

{

	if ((p == current) ||

	    (p->flags & PF_NOFREEZE))

		return 0;

	return 1;

}



static int try_to_freeze_tasks(bool sig_only)

{

	struct task_struct *g, *p;
@@ -52,10 +44,7 @@ static int try_to_freeze_tasks(bool sig_only) 
		todo = 0;

		read_lock(&tasklist_lock);

		do_each_thread(g, p) {

			if (frozen(p) || !freezable(p))

				continue;



			if (!freeze_task(p, sig_only))

			if (p == current || !freeze_task(p, sig_only))

				continue;



			/*
@@ -181,9 +170,6 @@ void thaw_processes(void) 


	read_lock(&tasklist_lock);

	do_each_thread(g, p) {

		if (!freezable(p))

			continue;



		if (cgroup_freezing_or_frozen(p))

			continue;