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: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 250def0..3251cc9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2535,7 +2535,7 @@
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 @@
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 @@
*/
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 @@
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 @@
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;