path: root/kernel/pid.c
diff options
authorTetsuo Handa <>2010-06-26 01:08:19 +0900
committerPaul E. McKenney <>2010-08-19 17:18:02 -0700
commit4221a9918e38b7494cee341dda7b7b4bb8c04bde (patch)
treeb79ed7629dd526a9c54dc116b7943cc496b3c19e /kernel/pid.c
parent394f99a9007d4274f7076bb8553ab0ff9707688b (diff)
Add RCU check for find_task_by_vpid().
find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to commit 3120438 "rcu: Disable lockdep checking in RCU list-traversal primitives", we are currently unable to catch "find_task_by_vpid() with tasklist_lock held but RCU lock not held" errors due to the RCU-lockdep checks being suppressed in the RCU variants of the struct list_head traversals. This commit therefore places an explicit check for being in an RCU read-side critical section in find_task_by_pid_ns(). =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:386 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 1 lock held by rc.sysinit/1102: #0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160 stack backtrace: Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1 Call Trace: [<c105e714>] lockdep_rcu_dereference+0x94/0xb0 [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70 [<c104b4e8>] find_task_by_vpid+0x18/0x20 [<c1048347>] sys_setpgid+0x47/0x160 [<c1002b50>] sysenter_do_call+0x12/0x36 Commit updated to use a new rcu_lockdep_assert() exported API rather than the old internal __do_rcu_dereference(). Signed-off-by: Tetsuo Handa <> Signed-off-by: Paul E. McKenney <> Reviewed-by: Josh Triplett <>
Diffstat (limited to 'kernel/pid.c')
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index 0f90c2f713f1..39b65b69584f 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -416,6 +416,7 @@ EXPORT_SYMBOL(pid_task);
struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
+ rcu_lockdep_assert(rcu_read_lock_held());
return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);