Re: [PATCH] fix get_jiffies_64 to work on voyager

[Andrew Morton <akpm@osdl.org>]

James Bottomley <James.Bottomley@SteelEye.com> wrote:
>
> This patch
> 
> 
>  ChangeSet@1.1534.5.2, 2003-12-30 15:40:23-08:00, akpm@osdl.org
>    [PATCH] ia32 jiffy wrapping fixes
> 
>  Causes the voyager boot to hang.  The problem is this change:
> 
>  --- a/arch/i386/kernel/timers/timer_tsc.c       Tue Jan  6 09:57:34 2004
>  +++ b/arch/i386/kernel/timers/timer_tsc.c       Tue Jan  6 09:57:34 2004
>  @@ -141,7 +140,7 @@
>   #ifndef CONFIG_NUMA
>          if (!use_tsc)
>   #endif
>  -               return (unsigned long long)jiffies * (1000000000 / HZ);
>  +               return (unsigned long long)get_jiffies_64() *
>  (1000000000 / HZ);

Hm, OK.  I hit the same deadlock when running with the "don't require TSCs
to be synchronised in sched_clock()" patch from -mm.  The fix for that is
below.  I shall accelerate it.

--- 25/arch/i386/kernel/timers/timer_tsc.c~sched_clock-2.6.0-A1-deadlock-fix	2003-12-30 00:45:09.000000000 -0800
+++ 25-akpm/arch/i386/kernel/timers/timer_tsc.c	2003-12-30 00:45:09.000000000 -0800
@@ -140,7 +140,8 @@ unsigned long long sched_clock(void)
 #ifndef CONFIG_NUMA
 	if (!use_tsc)
 #endif
-		return (unsigned long long)get_jiffies_64() * (1000000000 / HZ);
+		/* jiffies might overflow but this is not a big deal here */
+		return (unsigned long long)jiffies * (1000000000 / HZ);
 
 	/* Read the Time Stamp Counter */
 	rdtscll(this_offset);

_