From cdcd629869fabcd38ebd24a03b0a05ec1cbcafb0 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 2 Jan 2012 17:02:18 +0000 Subject: [PATCH] x86: Fix and improve cmpxchg_double{,_local}() Just like the per-CPU ones they had several problems/shortcomings: Only the first memory operand was mentioned in the asm() operands, and the 2x64-bit version didn't have a memory clobber while the 2x32-bit one did. The former allowed the compiler to not recognize the need to re-load the data in case it had it cached in some register, while the latter was overly destructive. The types of the local copies of the old and new values were incorrect (the types of the pointed-to variables should be used here, to make sure the respective old/new variable types are compatible). The __dummy/__junk variables were pointless, given that local copies of the inputs already existed (and can hence be used for discarded outputs). The 32-bit variant of cmpxchg_double_local() referenced cmpxchg16b_local(). At once also: - change the return value type to what it really is: 'bool' - unify 32- and 64-bit variants - abstract out the common part of the 'normal' and 'local' variants Signed-off-by: Jan Beulich Cc: Christoph Lameter Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/4F01F12A020000780006A19B@nat28.tlf.novell.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/cmpxchg.h | 23 ++++++++++++++++ arch/x86/include/asm/cmpxchg_32.h | 46 ------------------------------- arch/x86/include/asm/cmpxchg_64.h | 43 ----------------------------- mm/slub.c | 4 +-- 4 files changed, 25 insertions(+), 91 deletions(-) diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h index 5488e10b9dba..0c9fa2745f13 100644 --- a/arch/x86/include/asm/cmpxchg.h +++ b/arch/x86/include/asm/cmpxchg.h @@ -207,4 +207,27 @@ extern void __add_wrong_size(void) #define add_smp(ptr, inc) __add((ptr), (inc), LOCK_PREFIX) #define add_sync(ptr, inc) __add((ptr), (inc), "lock; ") +#define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2) \ +({ \ + bool __ret; \ + __typeof__(*(p1)) __old1 = (o1), __new1 = (n1); \ + __typeof__(*(p2)) __old2 = (o2), __new2 = (n2); \ + BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long)); \ + BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long)); \ + VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long))); \ + VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2)); \ + asm volatile(pfx "cmpxchg%c4b %2; sete %0" \ + : "=a" (__ret), "+d" (__old2), \ + "+m" (*(p1)), "+m" (*(p2)) \ + : "i" (2 * sizeof(long)), "a" (__old1), \ + "b" (__new1), "c" (__new2)); \ + __ret; \ +}) + +#define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ + __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2) + +#define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \ + __cmpxchg_double(, p1, p2, o1, o2, n1, n2) + #endif /* ASM_X86_CMPXCHG_H */ diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h index fbebb07dd80b..53f4b219336b 100644 --- a/arch/x86/include/asm/cmpxchg_32.h +++ b/arch/x86/include/asm/cmpxchg_32.h @@ -166,52 +166,6 @@ static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old, #endif -#define cmpxchg8b(ptr, o1, o2, n1, n2) \ -({ \ - char __ret; \ - __typeof__(o2) __dummy; \ - __typeof__(*(ptr)) __old1 = (o1); \ - __typeof__(o2) __old2 = (o2); \ - __typeof__(*(ptr)) __new1 = (n1); \ - __typeof__(o2) __new2 = (n2); \ - asm volatile(LOCK_PREFIX "cmpxchg8b %2; setz %1" \ - : "=d"(__dummy), "=a" (__ret), "+m" (*ptr)\ - : "a" (__old1), "d"(__old2), \ - "b" (__new1), "c" (__new2) \ - : "memory"); \ - __ret; }) - - -#define cmpxchg8b_local(ptr, o1, o2, n1, n2) \ -({ \ - char __ret; \ - __typeof__(o2) __dummy; \ - __typeof__(*(ptr)) __old1 = (o1); \ - __typeof__(o2) __old2 = (o2); \ - __typeof__(*(ptr)) __new1 = (n1); \ - __typeof__(o2) __new2 = (n2); \ - asm volatile("cmpxchg8b %2; setz %1" \ - : "=d"(__dummy), "=a"(__ret), "+m" (*ptr)\ - : "a" (__old), "d"(__old2), \ - "b" (__new1), "c" (__new2), \ - : "memory"); \ - __ret; }) - - -#define cmpxchg_double(ptr, o1, o2, n1, n2) \ -({ \ - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ - VM_BUG_ON((unsigned long)(ptr) % 8); \ - cmpxchg8b((ptr), (o1), (o2), (n1), (n2)); \ -}) - -#define cmpxchg_double_local(ptr, o1, o2, n1, n2) \ -({ \ - BUILD_BUG_ON(sizeof(*(ptr)) != 4); \ - VM_BUG_ON((unsigned long)(ptr) % 8); \ - cmpxchg16b_local((ptr), (o1), (o2), (n1), (n2)); \ -}) - #define system_has_cmpxchg_double() cpu_has_cx8 #endif /* _ASM_X86_CMPXCHG_32_H */ diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h index 285da02c38fa..614be87f1a9b 100644 --- a/arch/x86/include/asm/cmpxchg_64.h +++ b/arch/x86/include/asm/cmpxchg_64.h @@ -20,49 +20,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 val) cmpxchg_local((ptr), (o), (n)); \ }) -#define cmpxchg16b(ptr, o1, o2, n1, n2) \ -({ \ - char __ret; \ - __typeof__(o2) __junk; \ - __typeof__(*(ptr)) __old1 = (o1); \ - __typeof__(o2) __old2 = (o2); \ - __typeof__(*(ptr)) __new1 = (n1); \ - __typeof__(o2) __new2 = (n2); \ - asm volatile(LOCK_PREFIX "cmpxchg16b %2;setz %1" \ - : "=d"(__junk), "=a"(__ret), "+m" (*ptr) \ - : "b"(__new1), "c"(__new2), \ - "a"(__old1), "d"(__old2)); \ - __ret; }) - - -#define cmpxchg16b_local(ptr, o1, o2, n1, n2) \ -({ \ - char __ret; \ - __typeof__(o2) __junk; \ - __typeof__(*(ptr)) __old1 = (o1); \ - __typeof__(o2) __old2 = (o2); \ - __typeof__(*(ptr)) __new1 = (n1); \ - __typeof__(o2) __new2 = (n2); \ - asm volatile("cmpxchg16b %2;setz %1" \ - : "=d"(__junk), "=a"(__ret), "+m" (*ptr) \ - : "b"(__new1), "c"(__new2), \ - "a"(__old1), "d"(__old2)); \ - __ret; }) - -#define cmpxchg_double(ptr, o1, o2, n1, n2) \ -({ \ - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ - VM_BUG_ON((unsigned long)(ptr) % 16); \ - cmpxchg16b((ptr), (o1), (o2), (n1), (n2)); \ -}) - -#define cmpxchg_double_local(ptr, o1, o2, n1, n2) \ -({ \ - BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ - VM_BUG_ON((unsigned long)(ptr) % 16); \ - cmpxchg16b_local((ptr), (o1), (o2), (n1), (n2)); \ -}) - #define system_has_cmpxchg_double() cpu_has_cx16 #endif /* _ASM_X86_CMPXCHG_64_H */ diff --git a/mm/slub.c b/mm/slub.c index ed3334d9b6da..09ccee8fb58e 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -368,7 +368,7 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page VM_BUG_ON(!irqs_disabled()); #ifdef CONFIG_CMPXCHG_DOUBLE if (s->flags & __CMPXCHG_DOUBLE) { - if (cmpxchg_double(&page->freelist, + if (cmpxchg_double(&page->freelist, &page->counters, freelist_old, counters_old, freelist_new, counters_new)) return 1; @@ -402,7 +402,7 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page, { #ifdef CONFIG_CMPXCHG_DOUBLE if (s->flags & __CMPXCHG_DOUBLE) { - if (cmpxchg_double(&page->freelist, + if (cmpxchg_double(&page->freelist, &page->counters, freelist_old, counters_old, freelist_new, counters_new)) return 1; -- GitLab