sh: fix xtime_lock deadlocking.

[safe/jmp/linux-2.6] / arch / sh / kernel / time_32.c

diff --git a/arch/sh/kernel/time_32.c b/arch/sh/kernel/time_32.c
index 2bc04bf..7281342 100644 (file)
--- 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 */