Revert recent SMP timer changes - they cause deadlocks

Cset exclude: mingo@elte.hu[torvalds]|ChangeSet|20031012025453|05000

diff --git a/kernel/timer.c b/kernel/timer.c
index eb7df932e11a0a6ec23739a754eb4e87f079f245..176d2c3215b4e8261dc03bc44449ba898047088d 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -315,30 +315,23 @@ EXPORT_SYMBOL(del_timer);
  * the timer it also makes sure the handler has finished executing on other
  * CPUs.
  *
- * Synchronization rules: callers must prevent restarting of the timer
- * (except restarting the timer from the timer function itself), otherwise
- * this function is meaningless. It must not be called from interrupt
- * contexts. Upon exit the timer is not queued and the handler is not
- * running on any CPU.
+ * Synchronization rules: callers must prevent restarting of the timer,
+ * otherwise this function is meaningless. It must not be called from
+ * interrupt contexts. Upon exit the timer is not queued and the handler
+ * is not running on any CPU.
  *
- * The function returns the number of times it has deactivated a pending
- * timer.
+ * The function returns whether it has deactivated a pending timer or not.
  */
 int del_timer_sync(struct timer_list *timer)
 {
-       int i, ret = 0, again;
-       unsigned long flags;
        tvec_base_t *base;
+       int i, ret = 0;
 
        check_timer(timer);
 
 del_again:
        ret += del_timer(timer);
 
-       /*
-        * First do a lighter but racy check, whether the
-        * timer is running on any other CPU:
-        */
        for (i = 0; i < NR_CPUS; i++) {
                if (!cpu_online(i))
                        continue;
@@ -352,33 +345,8 @@ del_again:
                        break;
                }
        }
-
-       /*
-        * Do a heavy but race-free re-check to make sure both that
-        * the timer is neither running nor pending:
-        */
-       again = 0;
-       local_irq_save(flags);
-
-       for (i = 0; i < NR_CPUS; i++)
-               if (cpu_online(i))
-                       spin_lock(&per_cpu(tvec_bases, i).lock);
-
+       smp_rmb();
        if (timer_pending(timer))
-               again = 1;
-       else
-               for (i = 0; i < NR_CPUS; i++)
-                       if (cpu_online(i) &&
-                               (per_cpu(tvec_bases, i).running_timer == timer))
-                                       again = 1;
-
-       for (i = 0; i < NR_CPUS; i++)
-               if (cpu_online(i))
-                       spin_unlock(&per_cpu(tvec_bases, i).lock);
-
-       local_irq_restore(flags);
-
-       if (again)
                goto del_again;
 
        return ret;