sched: Use lockdep-based checking on rcu_dereference()

[net-next-2.6.git] / kernel / exit.c

diff --git a/kernel/exit.c b/kernel/exit.c
index 546774a31a66752a698faa02c4e54f7c39fbef9e..45ed043b8bf59b8704b7cc13f19b1b13824b7ce4 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -85,7 +85,9 @@ static void __exit_signal(struct task_struct *tsk)
        BUG_ON(!sig);
        BUG_ON(!atomic_read(&sig->count));
 
-       sighand = rcu_dereference(tsk->sighand);
+       sighand = rcu_dereference_check(tsk->sighand,
+                                       rcu_read_lock_held() ||
+                                       lockdep_is_held(&tasklist_lock));
        spin_lock(&sighand->siglock);
 
        posix_cpu_timers_exit(tsk);
@@ -170,8 +172,10 @@ void release_task(struct task_struct * p)
 repeat:
        tracehook_prepare_release_task(p);
        /* don't need to get the RCU readlock here - the process is dead and
-        * can't be modifying its own credentials */
+        * can't be modifying its own credentials. But shut RCU-lockdep up */
+       rcu_read_lock();
        atomic_dec(&__task_cred(p)->user->processes);
+       rcu_read_unlock();
 
        proc_flush_task(p);
 
@@ -473,9 +477,11 @@ static void close_files(struct files_struct * files)
        /*
         * It is safe to dereference the fd table without RCU or
         * ->file_lock because this is the last reference to the
-        * files structure.
+        * files structure.  But use RCU to shut RCU-lockdep up.
         */
+       rcu_read_lock();
        fdt = files_fdtable(files);
+       rcu_read_unlock();
        for (;;) {
                unsigned long set;
                i = j * __NFDBITS;
@@ -521,10 +527,12 @@ void put_files_struct(struct files_struct *files)
                 * at the end of the RCU grace period. Otherwise,
                 * you can free files immediately.
                 */
+               rcu_read_lock();
                fdt = files_fdtable(files);
                if (fdt != &files->fdtab)
                        kmem_cache_free(files_cachep, files);
                free_fdtable(fdt);
+               rcu_read_unlock();
        }
 }