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Subject[PATCH] make raid5 checksums preempt-safe, take two
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Linus,

The raid5 xor checksums use MMX/SSE state and are not preempt-safe.

Attached patch disables preemption in FPU_SAVE and XMMS_SAVE and
restores it in FPU_RESTORE and XMMS_RESTORE - preventing preemption
while in fp mode.

I fixed the silly errors in the previous patch; this ought to be right.

Patch is against 2.5.32-bk. Please, apply.

Robert Love

diff -urN linux-2.5.32/include/asm-i386/xor.h linux/include/asm-i386/xor.h
--- linux-2.5.32/include/asm-i386/xor.h Tue Aug 27 15:26:34 2002
+++ linux/include/asm-i386/xor.h Wed Aug 28 17:17:51 2002
@@ -20,6 +20,7 @@

#define FPU_SAVE \
do { \
+ preempt_disable(); \
if (!test_thread_flag(TIF_USEDFPU)) \
__asm__ __volatile__ (" clts;\n"); \
__asm__ __volatile__ ("fsave %0; fwait": "=m"(fpu_save[0])); \
@@ -30,6 +31,7 @@
__asm__ __volatile__ ("frstor %0": : "m"(fpu_save[0])); \
if (!test_thread_flag(TIF_USEDFPU)) \
stts(); \
+ preempt_enable(); \
} while (0)

#define LD(x,y) " movq 8*("#x")(%1), %%mm"#y" ;\n"
@@ -542,7 +544,8 @@
* Copyright (C) 1999 Zach Brown (with obvious credit due Ingo)
*/

-#define XMMS_SAVE \
+#define XMMS_SAVE do { \
+ preempt_disable(); \
__asm__ __volatile__ ( \
"movl %%cr0,%0 ;\n\t" \
"clts ;\n\t" \
@@ -552,9 +555,10 @@
"movups %%xmm3,0x30(%1) ;\n\t" \
: "=&r" (cr0) \
: "r" (xmm_save) \
- : "memory")
+ : "memory"); \
+} while(0)

-#define XMMS_RESTORE \
+#define XMMS_RESTORE do { \
__asm__ __volatile__ ( \
"sfence ;\n\t" \
"movups (%1),%%xmm0 ;\n\t" \
@@ -564,7 +568,9 @@
"movl %0,%%cr0 ;\n\t" \
: \
: "r" (cr0), "r" (xmm_save) \
- : "memory")
+ : "memory"); \
+ preempt_enable(); \
+} while(0)

#define ALIGN16 __attribute__((aligned(16)))

diff -urN linux-2.5.32/include/asm-x86_64/xor.h linux/include/asm-x86_64/xor.h
--- linux-2.5.32/include/asm-x86_64/xor.h Tue Aug 27 15:26:36 2002
+++ linux/include/asm-x86_64/xor.h Wed Aug 28 17:19:07 2002
@@ -37,8 +37,9 @@

/* Doesn't use gcc to save the XMM registers, because there is no easy way to
tell it to do a clts before the register saving. */
-#define XMMS_SAVE \
- asm volatile ( \
+#define XMMS_SAVE do { \
+ preempt_disable(); \
+ asm volatile ( \
"movq %%cr0,%0 ;\n\t" \
"clts ;\n\t" \
"movups %%xmm0,(%1) ;\n\t" \
@@ -47,10 +48,11 @@
"movups %%xmm3,0x30(%1) ;\n\t" \
: "=r" (cr0) \
: "r" (xmm_save) \
- : "memory")
+ : "memory"); \
+} while(0)

#define XMMS_RESTORE \
- asm volatile ( \
+ asm volatile ( \
"sfence ;\n\t" \
"movups (%1),%%xmm0 ;\n\t" \
"movups 0x10(%1),%%xmm1 ;\n\t" \
@@ -59,7 +61,9 @@
"movq %0,%%cr0 ;\n\t" \
: \
: "r" (cr0), "r" (xmm_save) \
- : "memory")
+ : "memory"); \
+ preempt_enable(); \
+} while(0)

#define OFFS(x) "16*("#x")"
#define PF_OFFS(x) "256+16*("#x")"
-
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