Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754656AbZJETeB (ORCPT ); Mon, 5 Oct 2009 15:34:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753589AbZJETeA (ORCPT ); Mon, 5 Oct 2009 15:34:00 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:48468 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753473AbZJETd7 (ORCPT ); Mon, 5 Oct 2009 15:33:59 -0400 Subject: Re: [PATCH] x86: Generate cmpxchg build failures From: Peter Zijlstra To: Linus Torvalds Cc: Eric Dumazet , Martin Schwidefsky , Thomas Gleixner , John Stultz , Linux Kernel Mailing List , Ingo Molnar , Arjan van de Ven In-Reply-To: References: <4AC060AE.1090401@gmail.com> <20090928191506.40b61793@mschwide.boeblingen.de.ibm.com> <4AC10365.7090802@gmail.com> <4AC2712C.4080901@gmail.com> <1254758425.26976.126.camel@twins> Content-Type: text/plain Date: Mon, 05 Oct 2009 21:33:07 +0200 Message-Id: <1254771187.21044.22.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 17096 Lines: 583 On Mon, 2009-10-05 at 12:16 -0700, Linus Torvalds wrote: > > On Mon, 5 Oct 2009, Peter Zijlstra wrote: > > > On Tue, 2009-09-29 at 14:17 -0700, Linus Torvalds wrote: > > > > > And regardless, we should fix the silent cmpxchg failure, even if it's > > > just a link-time failure or something. > > > > Something like the below? > > Looks good to me. This is also one of the cases where a macro will do > better than an inline function, since the return value depends on the size > of the pointer, and it doesn't do the whole 'unsigned long' thing any > more. Indeed, I was glad to see that go. > It should also be fairly easy to make this now just do a cmpxchg8b for the > 64-bit case (again, that wouldn't have worked sanely due to the fixed type > in the inline function version - expanding that size to 64-bit would have > been insane). But that's a separate issue (and maybe we don't want to do > it, due to the whole "it's not DMA-atomic" etc issue - we may be better > off with a build failure, and forcing people who really want 64-bit > accesses to use the explicit cmpxchg64 thing) Right, that would be a second patch if we think its a sane thing to do. > That said, I think that you should merge the insane three versions of this > macro into one. Having separate versions for "__[sync_|local_|]cmpxchg()" > is disgusting. I bet you can do it with a single macro, and just pass in > the LOCK_PREFIX (or empty, or "lock;") to that as needed. Rather than > duplicating it three times. You're right, what was I thinking doing all this copy/paste stuff. Here's a new one, still seems to build i386 and x86_64 defconfigs. Signed-off-by: Peter Zijlstra --- arch/x86/include/asm/cmpxchg_32.h | 218 ++++++++++++++--------------------- arch/x86/include/asm/cmpxchg_64.h | 234 ++++++++++++++---------------------- 2 files changed, 177 insertions(+), 275 deletions(-) diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h index ee1931b..720c3d4 100644 --- a/arch/x86/include/asm/cmpxchg_32.h +++ b/arch/x86/include/asm/cmpxchg_32.h @@ -8,14 +8,50 @@ * you need to test for the feature in boot_cpu_data. */ -#define xchg(ptr, v) \ - ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr)))) +extern void __xchg_wrong_size(void); + +/* + * Note: no "lock" prefix even on SMP: xchg always implies lock anyway + * Note 2: xchg has side effect, so that attribute volatile is necessary, + * but generally the primitive is invalid, *ptr is output argument. --ANK + */ struct __xchg_dummy { unsigned long a[100]; }; #define __xg(x) ((struct __xchg_dummy *)(x)) +#define __xchg(x, ptr, size) \ +({ \ + __typeof(*(ptr)) __x = (x); \ + switch (size) { \ + case 1: \ + asm volatile("xchgb %b0,%1" \ + : "=q" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + case 2: \ + asm volatile("xchgw %w0,%1" \ + : "=r" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + case 4: \ + asm volatile("xchgl %0,%1" \ + : "=r" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + default: \ + __xchg_wrong_size(); \ + } \ + __x; \ +}) + +#define xchg(ptr, v) \ + __xchg((v), (ptr), sizeof(*ptr)) + /* * The semantics of XCHGCMP8B are a bit strange, this is why * there is a loop and the loading of %%eax and %%edx has to @@ -71,57 +107,63 @@ static inline void __set_64bit_var(unsigned long long *ptr, (unsigned int)((value) >> 32)) \ : __set_64bit(ptr, ll_low((value)), ll_high((value)))) -/* - * Note: no "lock" prefix even on SMP: xchg always implies lock anyway - * Note 2: xchg has side effect, so that attribute volatile is necessary, - * but generally the primitive is invalid, *ptr is output argument. --ANK - */ -static inline unsigned long __xchg(unsigned long x, volatile void *ptr, - int size) -{ - switch (size) { - case 1: - asm volatile("xchgb %b0,%1" - : "=q" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 2: - asm volatile("xchgw %w0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 4: - asm volatile("xchgl %0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - } - return x; -} +extern void __cmpxchg_wrong_size(void); /* * Atomic compare and exchange. Compare OLD with MEM, if identical, * store NEW in MEM. Return the initial value in MEM. Success is * indicated by comparing RETURN with OLD. */ +#define __raw_cmpxchg(ptr, old, new, size, lock) \ +({ \ + __typeof__(*(ptr)) __ret; \ + __typeof__(*(ptr)) __old = (old); \ + __typeof__(*(ptr)) __new = (new); \ + switch (size) { \ + case 1: \ + asm volatile(lock "cmpxchgb %b1,%2" \ + : "=a"(__ret) \ + : "q"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + case 2: \ + asm volatile(lock "cmpxchgw %w1,%2" \ + : "=a"(__ret) \ + : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + case 4: \ + asm volatile(lock "cmpxchgl %1,%2" \ + : "=a"(__ret) \ + : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + default: \ + __cmpxchg_wrong_size(); \ + } \ + __ret; \ +}) + +#define __cmpxchg(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX) + +#define __sync_cmpxchg(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), "lock; ") + +#define __cmpxchg_local(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), "") #ifdef CONFIG_X86_CMPXCHG #define __HAVE_ARCH_CMPXCHG 1 -#define cmpxchg(ptr, o, n) \ - ((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o), \ - (unsigned long)(n), \ - sizeof(*(ptr)))) -#define sync_cmpxchg(ptr, o, n) \ - ((__typeof__(*(ptr)))__sync_cmpxchg((ptr), (unsigned long)(o), \ - (unsigned long)(n), \ - sizeof(*(ptr)))) -#define cmpxchg_local(ptr, o, n) \ - ((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o), \ - (unsigned long)(n), \ - sizeof(*(ptr)))) + +#define cmpxchg(ptr, old, new) \ + __cmpxchg((ptr), (old), (new), sizeof(*ptr)) + +#define sync_cmpxchg(ptr, old, new) \ + __sync_cmpxchg((ptr), (old), (new), sizeof(*ptr)) + +#define cmpxchg_local(ptr, old, new) \ + __cmpxchg_local((ptr), (old), (new), sizeof(*ptr)) #endif #ifdef CONFIG_X86_CMPXCHG64 @@ -133,94 +175,6 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, (unsigned long long)(n))) #endif -static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile(LOCK_PREFIX "cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile(LOCK_PREFIX "cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile(LOCK_PREFIX "cmpxchgl %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} - -/* - * Always use locked operations when touching memory shared with a - * hypervisor, since the system may be SMP even if the guest kernel - * isn't. - */ -static inline unsigned long __sync_cmpxchg(volatile void *ptr, - unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile("lock; cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile("lock; cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile("lock; cmpxchgl %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} - -static inline unsigned long __cmpxchg_local(volatile void *ptr, - unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile("cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile("cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile("cmpxchgl %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} - static inline unsigned long long __cmpxchg64(volatile void *ptr, unsigned long long old, unsigned long long new) diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h index 52de72e..d565670 100644 --- a/arch/x86/include/asm/cmpxchg_64.h +++ b/arch/x86/include/asm/cmpxchg_64.h @@ -3,9 +3,6 @@ #include /* Provides LOCK_PREFIX */ -#define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), \ - (ptr), sizeof(*(ptr)))) - #define __xg(x) ((volatile long *)(x)) static inline void set_64bit(volatile unsigned long *ptr, unsigned long val) @@ -15,167 +12,118 @@ static inline void set_64bit(volatile unsigned long *ptr, unsigned long val) #define _set_64bit set_64bit +extern void __xchg_wrong_size(void); +extern void __cmpxchg_wrong_size(void); + /* * Note: no "lock" prefix even on SMP: xchg always implies lock anyway * Note 2: xchg has side effect, so that attribute volatile is necessary, * but generally the primitive is invalid, *ptr is output argument. --ANK */ -static inline unsigned long __xchg(unsigned long x, volatile void *ptr, - int size) -{ - switch (size) { - case 1: - asm volatile("xchgb %b0,%1" - : "=q" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 2: - asm volatile("xchgw %w0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 4: - asm volatile("xchgl %k0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - case 8: - asm volatile("xchgq %0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) - : "memory"); - break; - } - return x; -} +#define __xchg(x, ptr, size) \ +({ \ + __typeof(*(ptr)) __x = (x); \ + switch (size) { \ + case 1: \ + asm volatile("xchgb %b0,%1" \ + : "=q" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + case 2: \ + asm volatile("xchgw %w0,%1" \ + : "=r" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + case 4: \ + asm volatile("xchgl %k0,%1" \ + : "=r" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + case 8: \ + asm volatile("xchgq %0,%1" \ + : "=r" (__x) \ + : "m" (*__xg(ptr)), "0" (__x) \ + : "memory"); \ + break; \ + default: \ + __xchg_wrong_size(); \ + } \ + __x; \ +}) + +#define xchg(ptr, v) \ + __xchg((v), (ptr), sizeof(*ptr)) + +#define __HAVE_ARCH_CMPXCHG 1 /* * Atomic compare and exchange. Compare OLD with MEM, if identical, * store NEW in MEM. Return the initial value in MEM. Success is * indicated by comparing RETURN with OLD. */ +#define __raw_cmpxchg(ptr, old, new, size, lock) \ +({ \ + __typeof__(*(ptr)) __ret; \ + __typeof__(*(ptr)) __old = (old); \ + __typeof__(*(ptr)) __new = (new); \ + switch (size) { \ + case 1: \ + asm volatile(lock "cmpxchgb %b1,%2" \ + : "=a"(__ret) \ + : "q"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + case 2: \ + asm volatile(lock "cmpxchgw %w1,%2" \ + : "=a"(__ret) \ + : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + case 4: \ + asm volatile(lock "cmpxchgl %k1,%2" \ + : "=a"(__ret) \ + : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + case 8: \ + asm volatile(lock "cmpxchgq %1,%2" \ + : "=a"(__ret) \ + : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + : "memory"); \ + break; \ + default: \ + __cmpxchg_wrong_size(); \ + } \ + __ret; \ +}) -#define __HAVE_ARCH_CMPXCHG 1 +#define __cmpxchg(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX) -static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile(LOCK_PREFIX "cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile(LOCK_PREFIX "cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile(LOCK_PREFIX "cmpxchgl %k1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 8: - asm volatile(LOCK_PREFIX "cmpxchgq %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} +#define __sync_cmpxchg(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), "lock; ") -/* - * Always use locked operations when touching memory shared with a - * hypervisor, since the system may be SMP even if the guest kernel - * isn't. - */ -static inline unsigned long __sync_cmpxchg(volatile void *ptr, - unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile("lock; cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile("lock; cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile("lock; cmpxchgl %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} +#define __cmpxchg_local(ptr, old, new, size) \ + __raw_cmpxchg((ptr), (old), (new), (size), "") -static inline unsigned long __cmpxchg_local(volatile void *ptr, - unsigned long old, - unsigned long new, int size) -{ - unsigned long prev; - switch (size) { - case 1: - asm volatile("cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 2: - asm volatile("cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 4: - asm volatile("cmpxchgl %k1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - case 8: - asm volatile("cmpxchgq %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); - return prev; - } - return old; -} +#define cmpxchg(ptr, old, new) \ + __cmpxchg((ptr), (old), (new), sizeof(*ptr)) + +#define sync_cmpxchg(ptr, old, new) \ + __sync_cmpxchg((ptr), (old), (new), sizeof(*ptr)) + +#define cmpxchg_local(ptr, old, new) \ + __cmpxchg_local((ptr), (old), (new), sizeof(*ptr)) -#define cmpxchg(ptr, o, n) \ - ((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o), \ - (unsigned long)(n), sizeof(*(ptr)))) #define cmpxchg64(ptr, o, n) \ ({ \ BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ cmpxchg((ptr), (o), (n)); \ }) -#define cmpxchg_local(ptr, o, n) \ - ((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o), \ - (unsigned long)(n), \ - sizeof(*(ptr)))) -#define sync_cmpxchg(ptr, o, n) \ - ((__typeof__(*(ptr)))__sync_cmpxchg((ptr), (unsigned long)(o), \ - (unsigned long)(n), \ - sizeof(*(ptr)))) + #define cmpxchg64_local(ptr, o, n) \ ({ \ BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/