[PATCH] Re: time() glitch on 2.4.18: solved

From: Jim Paris (jim@jtan.com)
Date: Tue Nov 05 2002 - 11:30:20 EST

> > Any comments?
>
> Have a play with it, if your idea works when you deliberately disturb it
> then send in a patch

This works well.

-jim

diff -urN linux-2.4.18/arch/i386/kernel/time.c linux-2.4.18-jim/arch/i386/kernel/time.c
--- linux-2.4.18/arch/i386/kernel/time.c Fri Mar 15 18:28:53 2002
+++ linux-2.4.18-jim/arch/i386/kernel/time.c Tue Nov 5 11:22:02 2002
@@ -501,6 +501,16 @@
 
                 count = inb_p(0x40); /* read the latched count */
                 count |= inb(0x40) << 8;
+
+ /* Any unpaired read will cause the above to swap MSB/LSB
+ forever. Try to detect this and reset the counter. */
+ if (count > LATCH) {
+ outb_p(0x34, 0x43);
+ outb_p(LATCH & 0xff, 0x40);
+ outb(LATCH >> 8, 0x40);
+ count = LATCH - 1;
+ }
+
                 spin_unlock(&i8253_lock);
 
                 count = ((LATCH-1) - count) * TICK_SIZE;
-
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