path: root/kernel/pid.c
diff options
authorPaul E. McKenney <>2011-05-24 08:31:09 -0700
committerPaul E. McKenney <>2011-09-28 21:36:37 -0700
commitb3fbab0571eb09746cc0283648165ec00efc8eb2 (patch)
tree63bc01cbf03a5df34a96af292a00df4a96dc148a /kernel/pid.c
parentd5988af53102f3b73e5e0788be024ccfa51869de (diff)
rcu: Restore checks for blocking in RCU read-side critical sections
Long ago, using TREE_RCU with PREEMPT would result in "scheduling while atomic" diagnostics if you blocked in an RCU read-side critical section. However, PREEMPT now implies TREE_PREEMPT_RCU, which defeats this diagnostic. This commit therefore adds a replacement diagnostic based on PROVE_RCU. Because rcu_lockdep_assert() and lockdep_rcu_dereference() are now being used for things that have nothing to do with rcu_dereference(), rename lockdep_rcu_dereference() to lockdep_rcu_suspicious() and add a third argument that is a string indicating what is suspicious. This third argument is passed in from a new third argument to rcu_lockdep_assert(). Update all calls to rcu_lockdep_assert() to add an informative third argument. Also, add a pair of rcu_lockdep_assert() calls from within rcu_note_context_switch(), one complaining if a context switch occurs in an RCU-bh read-side critical section and another complaining if a context switch occurs in an RCU-sched read-side critical section. These are present only if the PROVE_RCU kernel parameter is enabled. Finally, fix some checkpatch whitespace complaints in lockdep.c. Again, you must enable PROVE_RCU to see these new diagnostics. But you are enabling PROVE_RCU to check out new RCU uses in any case, aren't you? Signed-off-by: Paul E. McKenney <>
Diffstat (limited to 'kernel/pid.c')
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index e432057f3b21..8cafe7e72ad2 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -418,7 +418,9 @@ 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());
+ rcu_lockdep_assert(rcu_read_lock_held(),
+ "find_task_by_pid_ns() needs rcu_read_lock()"
+ " protection");
return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);