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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-07-29 15:04:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-29 19:10:35 -0700
commit887032670d47366a8c8f25396ea7c14b7b2cc620 (patch)
treee5f9ece5ab9239648e8d7051ccb9a217d92553d7 /include
parentf0d83679a8d471dc8b646919f70595d6fe8c9606 (diff)
cgroup avoid permanent sleep at rmdir
After commit ec64f51545fffbc4cb968f0cea56341a4b07e85a ("cgroup: fix frequent -EBUSY at rmdir"), cgroup's rmdir (especially against memcg) doesn't return -EBUSY by temporary ref counts. That commit expects all refs after pre_destroy() is temporary but...it wasn't. Then, rmdir can wait permanently. This patch tries to fix that and change followings. - set CGRP_WAIT_ON_RMDIR flag before pre_destroy(). - clear CGRP_WAIT_ON_RMDIR flag when the subsys finds racy case. if there are sleeping ones, wakes them up. - rmdir() sleeps only when CGRP_WAIT_ON_RMDIR flag is set. Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reported-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reviewed-by: Paul Menage <menage@google.com> Acked-by: Balbir Sigh <balbir@linux.vnet.ibm.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cgroup.h17
1 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 20411d2876f8..90bba9e62286 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -363,6 +363,23 @@ int cgroup_task_count(const struct cgroup *cgrp);
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
/*
+ * When the subsys has to access css and may add permanent refcnt to css,
+ * it should take care of racy conditions with rmdir(). Following set of
+ * functions, is for stop/restart rmdir if necessary.
+ * Because these will call css_get/put, "css" should be alive css.
+ *
+ * cgroup_exclude_rmdir();
+ * ...do some jobs which may access arbitrary empty cgroup
+ * cgroup_release_and_wakeup_rmdir();
+ *
+ * When someone removes a cgroup while cgroup_exclude_rmdir() holds it,
+ * it sleeps and cgroup_release_and_wakeup_rmdir() will wake him up.
+ */
+
+void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
+void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
+
+/*
* Control Group subsystem type.
* See Documentation/cgroups/cgroups.txt for details
*/