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SubjectAbout Celeron processor memory barrier problem
Hi,
I found that when I compiled the 2.4 kernel with the option
of Pentium III or Pentium 4 on a Celeron's PC, it could cause the
system hang at very beginning boot stage, and I found the problem
is cause by the fact that Intel Celeron doesn't have a real memory
barrier,but when you choose the Pentium III option, the kernel
assume the processor has a real memory barrier.
Here is a patch to fix it:

Merry Christmas :)
Michael Chen

diff -Nur linux/include/asm-i386/system.h linux.new/include/asm-i386/system.h
--- linux/include/asm-i386/system.h Mon Dec 11 19:26:39 2000
+++ linux.new/include/asm-i386/system.h Sat Dec 23 16:06:01 2000
@@ -274,7 +274,14 @@
#ifndef CONFIG_X86_XMM
#define mb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")
#else
-#define mb() __asm__ __volatile__ ("sfence": : :"memory")
+#define mb() do { \
+ if ( cpu_has_xmm ) { \
+ asm volatile("sfence": : :"memory"); \
+ } \
+ else { \
+ asm volatile("lock; addl $0,0(%%esp)": : :"memory"); \
+ } \
+} while (0)
#endif
#define rmb() mb()
#define wmb() __asm__ __volatile__ ("": : :"memory")
diff -Nur linux/include/linux/tqueue.h linux.new/include/linux/tqueue.h
--- linux/include/linux/tqueue.h Sat Dec 23 16:16:44 2000
+++ linux.new/include/linux/tqueue.h Sat Dec 23 16:06:01 2000
@@ -17,6 +17,7 @@
#include <linux/list.h>
#include <asm/bitops.h>
#include <asm/system.h>
+#include <asm/processor.h>

/*
* New proposed "bottom half" handlers:
diff -Nur linux/include/asm-i386/system.h linux.new/include/asm-i386/system.h
--- linux/include/asm-i386/system.h Mon Dec 11 19:26:39 2000
+++ linux.new/include/asm-i386/system.h Sat Dec 23 16:06:01 2000
@@ -274,7 +274,14 @@
#ifndef CONFIG_X86_XMM
#define mb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")
#else
-#define mb() __asm__ __volatile__ ("sfence": : :"memory")
+#define mb() do { \
+ if ( cpu_has_xmm ) { \
+ asm volatile("sfence": : :"memory"); \
+ } \
+ else { \
+ asm volatile("lock; addl $0,0(%%esp)": : :"memory"); \
+ } \
+} while (0)
#endif
#define rmb() mb()
#define wmb() __asm__ __volatile__ ("": : :"memory")
diff -Nur linux/include/linux/tqueue.h linux.new/include/linux/tqueue.h
--- linux/include/linux/tqueue.h Sat Dec 23 16:16:44 2000
+++ linux.new/include/linux/tqueue.h Sat Dec 23 16:06:01 2000
@@ -17,6 +17,7 @@
#include <linux/list.h>
#include <asm/bitops.h>
#include <asm/system.h>
+#include <asm/processor.h>

/*
* New proposed "bottom half" handlers:

-
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