diff options
| author | Tejun Heo <tj@kernel.org> | 2012-10-16 15:03:14 -0700 |
|---|---|---|
| committer | Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> | 2012-12-24 16:44:33 -0200 |
| commit | c7c467a1e121c6cc23afd2807ae5d106f3da7d91 (patch) | |
| tree | 7cccc593362a79d2db9844ee0ad4e7ac2f66607a /include/linux | |
| parent | 97df6fd06f0c5fdda5e6084fd5452360a9fc2b31 (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>
[ herton: backport to 3.5, CGROUP_BUILTIN_SUBSYS_COUNT is still present,
move the same code in cgroup_fork_callbacks over to cgroup_post_fork ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/cgroup.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index d3f5fba2c159..986b06a87b2c 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -33,7 +33,6 @@ 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, |