diff options
| author | Ben Blum <[email protected]> | 2011-11-02 13:38:05 -0700 |
|---|---|---|
| committer | Linus Torvalds <[email protected]> | 2011-11-02 16:06:59 -0700 |
| commit | 33ef6b6984403a688189317ef46bb3caab3b70e0 (patch) | |
| tree | 43dff6dd0150b34ce69b1d681c92659c9b20eb5c | |
| parent | 434a964daa14b9db083ce20404a4a2add54d037a (diff) | |
cgroups: more safe tasklist locking in cgroup_attach_proc
Fix unstable tasklist locking in cgroup_attach_proc.
According to this thread - https://lkml.org/lkml/2011/7/27/243 - RCU is
not sufficient to guarantee the tasklist is stable w.r.t. de_thread and
exit. Taking tasklist_lock for reading, instead of rcu_read_lock, ensures
proper exclusion.
Signed-off-by: Ben Blum <[email protected]>
Acked-by: Paul Menage <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Neil Brown <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
| -rw-r--r-- | kernel/cgroup.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 453100a4159d..64b0e73402df 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2027,7 +2027,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) goto out_free_group_list; /* prevent changes to the threadgroup list while we take a snapshot. */ - rcu_read_lock(); + read_lock(&tasklist_lock); if (!thread_group_leader(leader)) { /* * a race with de_thread from another thread's exec() may strip @@ -2036,7 +2036,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) * throw this task away and try again (from cgroup_procs_write); * this is "double-double-toil-and-trouble-check locking". */ - rcu_read_unlock(); + read_unlock(&tasklist_lock); retval = -EAGAIN; goto out_free_group_list; } @@ -2057,7 +2057,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) } while_each_thread(leader, tsk); /* remember the number of threads in the array for later. */ group_size = i; - rcu_read_unlock(); + read_unlock(&tasklist_lock); /* * step 1: check that we can legitimately attach to the cgroup. |