[PATCH] Work around for periodic do_gettimeofday hang

[James Bottomley <James.Bottomley@SteelEye.com>]

On the voyager systems particularly (but also on some of my slower
parisc boxes) I periodically get hangs where the system just seems to
stop (although it does remain able to execute alt-sysrq).  The traces
always seem to implicate do_gettimeofday in the xtime seqlock.

I've not been able to trace an exact cause for this, but it does seem to
be pretty much eliminated by lowering the clock speed to 100HZ.  I
propose the following patch to do this for the slower intel processors
(basically pentiums and below)

James

--

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

===== include/asm-i386/param.h 1.6 vs edited =====
--- 1.6/include/asm-i386/param.h	2004-06-24 03:55:46 -05:00
+++ edited/include/asm-i386/param.h	2004-11-22 18:36:42 -06:00
@@ -1,8 +1,15 @@
 #ifndef _ASMi386_PARAM_H
 #define _ASMi386_PARAM_H
 
+#include <linux/config.h>
+
 #ifdef __KERNEL__
-# define HZ		1000		/* Internal kernel timer frequency */
+# if defined(CONFIG_M386) || defined(CONFIG_M486) || defined(CONFIG_M586) \
+     || defined(CONFIG_M586TSC) || defined(CONFIG_M586MMX)
+#  define HZ		100
+# else
+#  define HZ		1000		/* Internal kernel timer frequency */
+# endif
 # define USER_HZ	100		/* .. some user interfaces are in "ticks" */
 # define CLOCKS_PER_SEC		(USER_HZ)	/* like times() */
 #endif