[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>

diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index 42c94c771afbe519ba538701be327a541463667b..51273b7297a76223f0a0b4035d3af21e1534e83b 100644 (file)
--- 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.