cgroups: add cpu_relax() calls in css_tryget() and cgroup_clear_css_refs() (804b3c28) · Commits · 戴 / test

include/linux/cgroup.h

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -99,6 +99,7 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
	while (!atomic_inc_not_zero(&css->refcnt)) {		while (!atomic_inc_not_zero(&css->refcnt)) {
	if (test_bit(CSS_REMOVED, &css->flags))		if (test_bit(CSS_REMOVED, &css->flags))
	return false;		return false;
			cpu_relax();
	}		}
	return true;		return true;
	}		}

+5 −2

Original line number	Original line	Diff line number	Diff line
	@@ -2509,7 +2509,7 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp)
	for_each_subsys(cgrp->root, ss) {		for_each_subsys(cgrp->root, ss) {
	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
	int refcnt;		int refcnt;
	do {		while (1) {
	/* We can only remove a CSS with a refcnt==1 */		/* We can only remove a CSS with a refcnt==1 */
	refcnt = atomic_read(&css->refcnt);		refcnt = atomic_read(&css->refcnt);
	if (refcnt > 1) {		if (refcnt > 1) {
	@@ -2523,7 +2523,10 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp)
	* css_tryget() to spin until we set the		* css_tryget() to spin until we set the
	* CSS_REMOVED bits or abort		* CSS_REMOVED bits or abort
	*/		*/
	} while (atomic_cmpxchg(&css->refcnt, refcnt, 0) != refcnt);		if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
			break;
			cpu_relax();
			}
	}		}
	done:		done:
	for_each_subsys(cgrp->root, ss) {		for_each_subsys(cgrp->root, ss) {