[MIPS] Protect more of timer_interrupt() by xtime_lock.

    
From Dave Johnson <djohnson+linuxmips@sw.starentnetworks.com>:

* do_timer() expects the arch-specific handler to take the lock as it
  modifies jiffies[_64] and xtime.
* writing timerhi/lo in timer_interrupt() will mess up
  fixed_rate_gettimeoffset() which reads timerhi/lo.
    
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index 42c94c771afb..51273b7297a7 100644
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -424,6 +424,8 @@ irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
         unsigned long j;
         unsigned int count;
 
+        write_seqlock(&xtime_lock);
+
         count = mips_hpt_read();
         mips_timer_ack();
 
@@ -441,7 +443,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
          * CMOS clock accordingly every ~11 minutes. rtc_set_time() has to be
          * called as close as possible to 500 ms before the new second starts.
          */
-        write_seqlock(&xtime_lock);
         if (ntp_synced() &&
             xtime.tv_sec > last_rtc_update + 660 &&
             (xtime.tv_nsec / 1000) >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
@@ -453,7 +454,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
                         last_rtc_update = xtime.tv_sec - 600;
                 }
         }
-        write_sequnlock(&xtime_lock);
 
         /*
          * If jiffies has overflown in this timer_interrupt, we must
@@ -496,6 +496,8 @@ irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
                 }
         }
 
+        write_sequnlock(&xtime_lock);
+
         /*
          * In UP mode, we call local_timer_interrupt() to do profiling
          * and process accouting.