Revert "remove false BUG_ON() from run_posix_cpu_timers()"

This reverts commit 3de463c7d9d58f8cf3395268230cb20a4c15bffa.

Roland has another patch that allows us to leave the BUG_ON() in place
by just making sure that the condition it tests for really is always
true.

That goes in next.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 26 insertions, 18 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 4897977a1f4b..3b25b182d2be 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -825,6 +825,14 @@ fastcall NORET_TYPE void do_exit(long code)
 
         tsk->flags |= PF_EXITING;
 
+        /*
+         * Make sure we don't try to process any timer firings
+         * while we are already exiting.
+         */
+        tsk->it_virt_expires = cputime_zero;
+        tsk->it_prof_expires = cputime_zero;
+        tsk->it_sched_expires = 0;
+
         if (unlikely(in_atomic()))
                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
                                 current->comm, current->pid,
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 383ba22f0b62..ea1aca5e7c2b 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1293,30 +1293,30 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 
 #undef  UNEXPIRED
 
+        BUG_ON(tsk->exit_state);
+
         /*
          * Double-check with locks held.
          */
         read_lock(&tasklist_lock);
-        if (likely(tsk->signal != NULL)) {
-                spin_lock(&tsk->sighand->siglock);
+        spin_lock(&tsk->sighand->siglock);
 
-                /*
-                 * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
-                 * all the timers that are firing, and put them on the firing list.
-                 */
-                check_thread_timers(tsk, &firing);
-                check_process_timers(tsk, &firing);
+        /*
+         * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
+         * all the timers that are firing, and put them on the firing list.
+         */
+        check_thread_timers(tsk, &firing);
+        check_process_timers(tsk, &firing);
 
-                /*
-                 * We must release these locks before taking any timer's lock.
-                 * There is a potential race with timer deletion here, as the
-                 * siglock now protects our private firing list.  We have set
-                 * the firing flag in each timer, so that a deletion attempt
-                 * that gets the timer lock before we do will give it up and
-                 * spin until we've taken care of that timer below.
-                 */
-                spin_unlock(&tsk->sighand->siglock);
-        }
+        /*
+         * We must release these locks before taking any timer's lock.
+         * There is a potential race with timer deletion here, as the
+         * siglock now protects our private firing list.  We have set
+         * the firing flag in each timer, so that a deletion attempt
+         * that gets the timer lock before we do will give it up and
+         * spin until we've taken care of that timer below.
+         */
+        spin_unlock(&tsk->sighand->siglock);
         read_unlock(&tasklist_lock);
 
         /*