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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>
This commit is contained in:
Tejun Heo 2014-05-13 12:11:00 -04:00
parent d37167ab7b
commit 7d331fa985
1 changed files with 9 additions and 9 deletions
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18
kernel/cgroup.c
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@ -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;