freezer: test freezable conditions while holding freezer_lock (85f1d476) · Commits · 戴 / test

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:

Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>

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;

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