Merge 'Linux v3.0' into Litmus

Some notes:
* Litmus^RT scheduling class is the topmost scheduling class
  (above stop_sched_class).
* scheduler_ipi() function (e.g., in smp_reschedule_interrupt())
  may increase IPI latencies.
* Added path into schedule() to quickly re-evaluate scheduling
  decision without becoming preemptive again. This used to be
  a standard path before the removal of BKL.

Conflicts:
	Makefile
	arch/arm/kernel/calls.S
	arch/arm/kernel/smp.c
	arch/x86/include/asm/unistd_32.h
	arch/x86/kernel/smp.c
	arch/x86/kernel/syscall_table_32.S
	include/linux/hrtimer.h
	kernel/printk.c
	kernel/sched.c
	kernel/sched_fair.c

1 files changed, 9 insertions, 4 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
index bd1d42b17cb2..7b01de98bb6a 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -17,7 +17,7 @@ static inline void frozen_process(void)
 {
         if (!unlikely(current->flags & PF_NOFREEZE)) {
                 current->flags |= PF_FROZEN;
-                wmb();
+                smp_wmb();
         }
         clear_freeze_flag(current);
 }
@@ -93,7 +93,7 @@ bool freeze_task(struct task_struct *p, bool sig_only)
          * the task as frozen and next clears its TIF_FREEZE.
          */
         if (!freezing(p)) {
-                rmb();
+                smp_rmb();
                 if (frozen(p))
                         return false;
 
@@ -104,8 +104,13 @@ bool freeze_task(struct task_struct *p, bool sig_only)
         }
 
         if (should_send_signal(p)) {
-                if (!signal_pending(p))
-                        fake_signal_wake_up(p);
+                fake_signal_wake_up(p);
+                /*
+                 * fake_signal_wake_up() goes through p's scheduler
+                 * lock and guarantees that TASK_STOPPED/TRACED ->
+                 * TASK_RUNNING transition can't race with task state
+                 * testing in try_to_freeze_tasks().
+                 */
         } else if (sig_only) {
                 return false;
         } else {