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authorTejun Heo <tj@kernel.org>2012-10-16 15:03:14 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-03-11 16:10:03 -0700
commit30ec268be37bdb5b1614cce40af8083f1a7c27f3 (patch)
tree0304a8573785798584cbd36ed30f69621410ba64 /include
parentf47929fd5093c4b5c134ff2b2811ae327102bafd (diff)
cgroup: cgroup_subsys->fork() should be called after the task is added to css_set
commit 5edee61edeaaebafe584f8fb7074c1ef4658596b upstream. cgroup core has a bug which violates a basic rule about event notifications - when a new entity needs to be added, you add that to the notification list first and then make the new entity conform to the current state. If done in the reverse order, an event happening inbetween will be lost. cgroup_subsys->fork() is invoked way before the new task is added to the css_set. Currently, cgroup_freezer is the only user of ->fork() and uses it to make new tasks conform to the current state of the freezer. If FROZEN state is requested while fork is in progress between cgroup_fork_callbacks() and cgroup_post_fork(), the child could escape freezing - the cgroup isn't frozen when ->fork() is called and the freezer couldn't see the new task on the css_set. This patch moves cgroup_subsys->fork() invocation to cgroup_post_fork() after the new task is added to the css_set. cgroup_fork_callbacks() is removed. Because now a task may be migrated during cgroup_subsys->fork(), freezer_fork() is updated so that it adheres to the usual RCU locking and the rather pointless comment on why locking can be different there is removed (if it doesn't make anything simpler, why even bother?). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rafael J. Wysocki <rjw@sisk.pl> [hq: Backported to 3.4: - Adjust context - Iterate over first CGROUP_BUILTIN_SUBSYS_COUNT elements of subsys] Signed-off-by: Qiang Huang <h.huangqiang@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cgroup.h1
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 5a85b3415c1b..398276dbfebf 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -32,7 +32,6 @@ extern int cgroup_lock_is_held(void);
extern bool cgroup_lock_live_group(struct cgroup *cgrp);
extern void cgroup_unlock(void);
extern void cgroup_fork(struct task_struct *p);
-extern void cgroup_fork_callbacks(struct task_struct *p);
extern void cgroup_post_fork(struct task_struct *p);
extern void cgroup_exit(struct task_struct *p, int run_callbacks);
extern int cgroupstats_build(struct cgroupstats *stats,