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Commit 7d331fa9 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: use restart_syscall() for retries after offline waits in cgroup_subtree_control_write() 



After waiting for a child to finish offline,
cgroup_subtree_control_write() jumps up to retry from after the input
parsing and active protection breaking.  This retry makes the
scheduled locking update - removal of cgroup_tree_mutex - more
difficult.  Let's simplify it by returning with restart_syscall() for
retries.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent d37167ab

kernel/cgroup.c

+9 −9
Original line number Diff line number Diff line
@@ -2535,7 +2535,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) 
static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css,

					struct cftype *cft, char *buffer)

{

	unsigned int enable_req = 0, disable_req = 0, enable, disable;

	unsigned int enable = 0, disable = 0;

	struct cgroup *cgrp = dummy_css->cgroup, *child;

	struct cgroup_subsys *ss;

	char *tok, *p;
@@ -2554,11 +2554,11 @@ static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css, 
				continue;



			if (*tok == '+') {

				enable_req |= 1 << ssid;

				disable_req &= ~(1 << ssid);

				enable |= 1 << ssid;

				disable &= ~(1 << ssid);

			} else if (*tok == '-') {

				disable_req |= 1 << ssid;

				enable_req &= ~(1 << ssid);

				disable |= 1 << ssid;

				enable &= ~(1 << ssid);

			} else {

				return -EINVAL;

			}
@@ -2576,9 +2576,6 @@ static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css, 
	 */

	cgroup_get(cgrp);

	kernfs_break_active_protection(cgrp->control_kn);

retry:

	enable = enable_req;

	disable = disable_req;



	mutex_lock(&cgroup_tree_mutex);
@@ -2608,7 +2605,9 @@ static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css, 
				schedule();

				finish_wait(&child->offline_waitq, &wait);

				cgroup_put(child);

				goto retry;



				ret = restart_syscall();

				goto out_unbreak;

			}



			/* unavailable or not enabled on the parent? */
@@ -2692,6 +2691,7 @@ static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css, 
	mutex_unlock(&cgroup_mutex);

out_unlock_tree:

	mutex_unlock(&cgroup_tree_mutex);

out_unbreak:

	kernfs_unbreak_active_protection(cgrp->control_kn);

	cgroup_put(cgrp);

	return ret;