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cgroups: make cgroup_path() RCU-safe

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Fix races between /proc/sched_debug by freeing cgroup objects via an RCU
callback.  Thus any cgroup reference obtained from an RCU-safe source will
remain valid during the RCU section.  Since dentries are also RCU-safe,
this allows us to traverse up the tree safely.

Additionally, make cgroup_path() check for a NULL cgrp->dentry to avoid
trying to report a path for a partially-created cgroup.

[lizf@cn.fujitsu.com: call deactive_super() in cgroup_diput()]
Signed-off-by: Paul Menage <menage@google.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Paul Menage
2009-01-07 18:07:44 -08:00
committed by Linus Torvalds
parent e7b80bb695
commit a47295e6bc
2 changed files with 25 additions and 10 deletions
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5
include/linux/cgroup.h
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@ -116,7 +116,7 @@ struct cgroup {
struct list_head children; /* my children */
struct cgroup *parent; /* my parent */
struct dentry *dentry; /* cgroup fs entry */
struct dentry *dentry; /* cgroup fs entry, RCU protected */
/* Private pointers for each registered subsystem */
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
@ -145,6 +145,9 @@ struct cgroup {
int pids_use_count;
/* Length of the current tasks_pids array */
int pids_length;
/* For RCU-protected deletion */
struct rcu_head rcu_head;
};
/* A css_set is a structure holding pointers to a set of