From: john stultz <johnstul@us.ibm.com>, Alexander Atanasov <alex@ssi.bg>
We want to make sure we update jiffies_p and count_p atomically. So I'm
inserting the spin_unlock_irqrestore() after we update count_p, rather then
just before.
25-akpm/arch/i386/kernel/timers/timer_pit.c | 9 ++++-----
1 files changed, 4 insertions(+), 5 deletions(-)
diff -puN arch/i386/kernel/timers/timer_pit.c~timer-pit-race-fix arch/i386/kernel/timers/timer_pit.c
--- 25/arch/i386/kernel/timers/timer_pit.c~timer-pit-race-fix Fri Apr 18 16:31:07 2003
+++ 25-akpm/arch/i386/kernel/timers/timer_pit.c Fri Apr 18 16:31:07 2003
@@ -54,7 +54,7 @@ static void delay_pit(unsigned long loop
}
-/* This function must be called with interrupts disabled
+/* This function must be called with xtime_lock held.
* It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
*
* However, the pc-audio speaker driver changes the divisor so that
@@ -93,7 +93,7 @@ static unsigned long get_offset_pit(void
static unsigned long jiffies_p = 0;
/*
- * cache volatile jiffies temporarily; we have IRQs turned off.
+ * cache volatile jiffies temporarily; we have xtime_lock.
*/
unsigned long jiffies_t;
@@ -119,8 +119,6 @@ static unsigned long get_offset_pit(void
count = LATCH - 1;
}
- spin_unlock_irqrestore(&i8253_lock, flags);
-
/*
* avoiding timer inconsistencies (they are rare, but they happen)...
* there are two kinds of problems that must be avoided here:
@@ -130,7 +128,6 @@ static unsigned long get_offset_pit(void
* (see c't 95/10 page 335 for Neptun bug.)
*/
-
if( jiffies_t == jiffies_p ) {
if( count > count_p ) {
/* the nutcase */
@@ -141,6 +138,8 @@ static unsigned long get_offset_pit(void
count_p = count;
+ spin_unlock_irqrestore(&i8253_lock, flags);
+
count = ((LATCH-1) - count) * TICK_SIZE;
count = (count + LATCH/2) / LATCH;
_