Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (44 commits)
  rcu: Fix accelerated GPs for last non-dynticked CPU
  rcu: Make non-RCU_PROVE_LOCKING rcu_read_lock_sched_held() understand boot
  rcu: Fix accelerated grace periods for last non-dynticked CPU
  rcu: Export rcu_scheduler_active
  rcu: Make rcu_read_lock_sched_held() take boot time into account
  rcu: Make lockdep_rcu_dereference() message less alarmist
  sched, cgroups: Fix module export
  rcu: Add RCU_CPU_STALL_VERBOSE to dump detailed per-task information
  rcu: Fix rcutorture mod_timer argument to delay one jiffy
  rcu: Fix deadlock in TREE_PREEMPT_RCU CPU stall detection
  rcu: Convert to raw_spinlocks
  rcu: Stop overflowing signed integers
  rcu: Use canonical URL for Mathieu's dissertation
  rcu: Accelerate grace period if last non-dynticked CPU
  rcu: Fix citation of Mathieu's dissertation
  rcu: Documentation update for CONFIG_PROVE_RCU
  security: Apply lockdep-based checking to rcu_dereference() uses
  idr: Apply lockdep-based diagnostics to rcu_dereference() uses
  radix-tree: Disable RCU lockdep checking in radix tree
  vfs: Abstract rcu_dereference_check for files-fdtable use
  ...

1 files changed, 11 insertions, 3 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 546774a31a66..45ed043b8bf5 100644
--- 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();
         }
 }