cgroup_freezer: simplify propagation of CGROUP_FROZEN clearing in freezer_attach() (599c963a) · Commits · 戴 / test

If one or more tasks get moved into a frozen css, the frozen state is cleared up from the destination css so that it can be reasserted once the migrated tasks are frozen. freezer_attach() implements this in two separate steps - clearing CGROUP_FROZEN on the target css while processing each task and propagating the clearing upwards after the task loop is done if necessary. This patch merges the two steps. Propagation now takes place inside the task loop. This simplifies the code and prepares it for the fix of multi-destination migration. Signed-off-by:

Tejun Heo <tj@kernel.org>

kernel/cgroup_freezer.c

+7 −10

Original line number	Diff line number	Diff line
		@@ -158,9 +158,7 @@ static void freezer_css_free(struct cgroup_subsys_state *css)
		static void freezer_attach(struct cgroup_subsys_state *new_css,
		struct cgroup_taskset *tset)
		{
		struct freezer *freezer = css_freezer(new_css);
		struct task_struct *task;
		bool clear_frozen = false;

		mutex_lock(&freezer_mutex);

		@@ -175,19 +173,18 @@ static void freezer_attach(struct cgroup_subsys_state *new_css,
		* be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
		*/
		cgroup_taskset_for_each(task, tset) {
		struct freezer *freezer = css_freezer(new_css);

		if (!(freezer->state & CGROUP_FREEZING)) {
		__thaw_task(task);
		} else {
		freeze_task(task);
		/* clear FROZEN and propagate upwards */
		while (freezer && (freezer->state & CGROUP_FROZEN)) {
		freezer->state &= ~CGROUP_FROZEN;
		clear_frozen = true;
		freezer = parent_freezer(freezer);
		}
		}

		/* propagate FROZEN clearing upwards */
		while (clear_frozen && (freezer = parent_freezer(freezer))) {
		freezer->state &= ~CGROUP_FROZEN;
		clear_frozen = freezer->state & CGROUP_FREEZING;
		}

		mutex_unlock(&freezer_mutex);

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