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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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