sh: fix xtime_lock deadlocking.

move update_process_times() out from under xtime_lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 15 insertions, 4 deletions

diff --git a/arch/sh/kernel/time_32.c b/arch/sh/kernel/time_32.c
index 2bc04bfee73..7281342c044 100644
--- a/arch/sh/kernel/time_32.c
+++ b/arch/sh/kernel/time_32.c
@@ -120,10 +120,6 @@ static long last_rtc_update;
  */
 void handle_timer_tick(void)
 {
-        do_timer(1);
-#ifndef CONFIG_SMP
-        update_process_times(user_mode(get_irq_regs()));
-#endif
         if (current->pid)
                 profile_tick(CPU_PROFILING);
 
@@ -133,6 +129,16 @@ void handle_timer_tick(void)
 #endif
 
         /*
+         * Here we are in the timer irq handler. We just have irqs locally
+         * disabled but we don't know if the timer_bh is running on the other
+         * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
+         * the irq version of write_lock because as just said we have irq
+         * locally disabled. -arca
+         */
+        write_seqlock(&xtime_lock);
+        do_timer(1);
+
+        /*
          * If we have an externally synchronized Linux clock, then update
          * RTC clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
          * called as close as possible to 500 ms before the new second starts.
@@ -147,6 +153,11 @@ void handle_timer_tick(void)
                         /* do it again in 60s */
                         last_rtc_update = xtime.tv_sec - 600;
         }
+        write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+        update_process_times(user_mode(get_irq_regs()));
+#endif
 }
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */