From b3ac891b67bd4b1fc728d1c784cad1212dea433d Mon Sep 17 00:00:00 2001 From: Luca Barbieri Date: Wed, 24 Feb 2010 10:54:22 +0100 Subject: x86: Add support for lock prefix in alternatives The current lock prefix UP/SMP alternative code doesn't allow LOCK_PREFIX to be used in alternatives code. This patch solves the problem by adding a new LOCK_PREFIX_ALTERNATIVE_PATCH macro that only records the lock prefix location but does not emit the prefix. The user of this macro can then start any alternative sequence with "lock" and have it UP/SMP patched. To make this work, the UP/SMP alternative code is changed to do the lock/DS prefix switching only if the byte actually contains a lock or DS prefix. Thus, if an alternative without the "lock" is selected, it will now do nothing instead of clobbering the code. Changes in v2: - Naming change - Change label to not conflict with alternatives Signed-off-by: Luca Barbieri LKML-Reference: <1267005265-27958-2-git-send-email-luca@luca-barbieri.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/alternative.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 3b5b828767b6..55fee12cea6d 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -28,12 +28,14 @@ */ #ifdef CONFIG_SMP -#define LOCK_PREFIX \ +#define LOCK_PREFIX_HERE \ ".section .smp_locks,\"a\"\n" \ _ASM_ALIGN "\n" \ - _ASM_PTR "661f\n" /* address */ \ + _ASM_PTR "671f\n" /* address */ \ ".previous\n" \ - "661:\n\tlock; " + "671:" + +#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " #else /* ! CONFIG_SMP */ #define LOCK_PREFIX "" -- cgit v1.2.1 From 9c76b38476b18c45f97098a10b0176b321eba3ea Mon Sep 17 00:00:00 2001 From: Luca Barbieri Date: Wed, 24 Feb 2010 10:54:23 +0100 Subject: x86-32: Allow UP/SMP lock replacement in cmpxchg64 Use the functionality just introduced in the previous patch: mark the lock prefixes in cmpxchg64 alternatives for UP removal. Changes in v2: - Naming change Signed-off-by: Luca Barbieri LKML-Reference: <1267005265-27958-3-git-send-email-luca@luca-barbieri.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/cmpxchg_32.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h index ffb9bb6b6c37..8859e12dd3cf 100644 --- a/arch/x86/include/asm/cmpxchg_32.h +++ b/arch/x86/include/asm/cmpxchg_32.h @@ -271,7 +271,8 @@ extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64); __typeof__(*(ptr)) __ret; \ __typeof__(*(ptr)) __old = (o); \ __typeof__(*(ptr)) __new = (n); \ - alternative_io("call cmpxchg8b_emu", \ + alternative_io(LOCK_PREFIX_HERE \ + "call cmpxchg8b_emu", \ "lock; cmpxchg8b (%%esi)" , \ X86_FEATURE_CX8, \ "=A" (__ret), \ -- cgit v1.2.1 From a7e926abc3adfbd2e5e20d2b46177adb4e313915 Mon Sep 17 00:00:00 2001 From: Luca Barbieri Date: Wed, 24 Feb 2010 10:54:25 +0100 Subject: x86-32: Rewrite 32-bit atomic64 functions in assembly This patch replaces atomic64_32.c with two assembly implementations, one for 386/486 machines using pushf/cli/popf and one for 586+ machines using cmpxchg8b. The cmpxchg8b implementation provides the following advantages over the current one: 1. Implements atomic64_add_unless, atomic64_dec_if_positive and atomic64_inc_not_zero 2. Uses the ZF flag changed by cmpxchg8b instead of doing a comparison 3. Uses custom register calling conventions that reduce or eliminate register moves to suit cmpxchg8b 4. Reads the initial value instead of using cmpxchg8b to do that. Currently we use lock xaddl and movl, which seems the fastest. 5. Does not use the lock prefix for atomic64_set 64-bit writes are already atomic, so we don't need that. We still need it for atomic64_read to avoid restoring a value changed in the meantime. 6. Allocates registers as well or better than gcc The 386 implementation provides support for 386 and 486 machines. 386/486 SMP is not supported (we dropped it), but such support can be added easily if desired. A pure assembly implementation is required due to the custom calling conventions, and desire to use %ebp in atomic64_add_return (we need 7 registers...), as well as the ability to use pushf/popf in the 386 code without an intermediate pop/push. The parameter names are changed to match the convention in atomic_64.h Changes in v3 (due to rebasing to tip/x86/asm): - Patches atomic64_32.h instead of atomic_32.h - Uses the CALL alternative mechanism from commit 1b1d9258181bae199dc940f4bd0298126b9a73d9 Changes in v2: - Merged 386 and cx8 support in the same patch - 386 support now done in assembly, C code no longer used at all - cmpxchg64 is used for atomic64_cmpxchg - stop using macros, use one-line inline functions instead - miscellanous changes and improvements Signed-off-by: Luca Barbieri LKML-Reference: <1267005265-27958-5-git-send-email-luca@luca-barbieri.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/atomic64_32.h | 278 ++++++++++++++++++++++++++++--------- 1 file changed, 211 insertions(+), 67 deletions(-) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h index 03027bf28de5..2a934aa19a43 100644 --- a/arch/x86/include/asm/atomic64_32.h +++ b/arch/x86/include/asm/atomic64_32.h @@ -14,109 +14,193 @@ typedef struct { #define ATOMIC64_INIT(val) { (val) } -extern u64 atomic64_cmpxchg(atomic64_t *ptr, u64 old_val, u64 new_val); +#ifdef CONFIG_X86_CMPXCHG64 +#define ATOMIC64_ALTERNATIVE_(f, g) "call atomic64_" #g "_cx8" +#else +#define ATOMIC64_ALTERNATIVE_(f, g) ALTERNATIVE("call atomic64_" #f "_386", "call atomic64_" #g "_cx8", X86_FEATURE_CX8) +#endif + +#define ATOMIC64_ALTERNATIVE(f) ATOMIC64_ALTERNATIVE_(f, f) + +/** + * atomic64_cmpxchg - cmpxchg atomic64 variable + * @p: pointer to type atomic64_t + * @o: expected value + * @n: new value + * + * Atomically sets @v to @n if it was equal to @o and returns + * the old value. + */ + +static inline long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n) +{ + return cmpxchg64(&v->counter, o, n); +} /** * atomic64_xchg - xchg atomic64 variable - * @ptr: pointer to type atomic64_t - * @new_val: value to assign + * @v: pointer to type atomic64_t + * @n: value to assign * - * Atomically xchgs the value of @ptr to @new_val and returns + * Atomically xchgs the value of @v to @n and returns * the old value. */ -extern u64 atomic64_xchg(atomic64_t *ptr, u64 new_val); +static inline long long atomic64_xchg(atomic64_t *v, long long n) +{ + long long o; + unsigned high = (unsigned)(n >> 32); + unsigned low = (unsigned)n; + asm volatile(ATOMIC64_ALTERNATIVE(xchg) + : "=A" (o), "+b" (low), "+c" (high) + : "S" (v) + : "memory" + ); + return o; +} /** * atomic64_set - set atomic64 variable - * @ptr: pointer to type atomic64_t - * @new_val: value to assign + * @v: pointer to type atomic64_t + * @n: value to assign * - * Atomically sets the value of @ptr to @new_val. + * Atomically sets the value of @v to @n. */ -extern void atomic64_set(atomic64_t *ptr, u64 new_val); +static inline void atomic64_set(atomic64_t *v, long long i) +{ + unsigned high = (unsigned)(i >> 32); + unsigned low = (unsigned)i; + asm volatile(ATOMIC64_ALTERNATIVE(set) + : "+b" (low), "+c" (high) + : "S" (v) + : "eax", "edx", "memory" + ); +} /** * atomic64_read - read atomic64 variable - * @ptr: pointer to type atomic64_t + * @v: pointer to type atomic64_t * - * Atomically reads the value of @ptr and returns it. + * Atomically reads the value of @v and returns it. */ -static inline u64 atomic64_read(atomic64_t *ptr) +static inline long long atomic64_read(atomic64_t *v) { - u64 res; - - /* - * Note, we inline this atomic64_t primitive because - * it only clobbers EAX/EDX and leaves the others - * untouched. We also (somewhat subtly) rely on the - * fact that cmpxchg8b returns the current 64-bit value - * of the memory location we are touching: - */ - asm volatile( - "mov %%ebx, %%eax\n\t" - "mov %%ecx, %%edx\n\t" - LOCK_PREFIX "cmpxchg8b %1\n" - : "=&A" (res) - : "m" (*ptr) - ); - - return res; -} - -extern u64 atomic64_read(atomic64_t *ptr); + long long r; + asm volatile(ATOMIC64_ALTERNATIVE(read) + : "=A" (r), "+c" (v) + : : "memory" + ); + return r; + } /** * atomic64_add_return - add and return - * @delta: integer value to add - * @ptr: pointer to type atomic64_t + * @i: integer value to add + * @v: pointer to type atomic64_t * - * Atomically adds @delta to @ptr and returns @delta + *@ptr + * Atomically adds @i to @v and returns @i + *@v */ -extern u64 atomic64_add_return(u64 delta, atomic64_t *ptr); +static inline long long atomic64_add_return(long long i, atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE(add_return) + : "+A" (i), "+c" (v) + : : "memory" + ); + return i; +} /* * Other variants with different arithmetic operators: */ -extern u64 atomic64_sub_return(u64 delta, atomic64_t *ptr); -extern u64 atomic64_inc_return(atomic64_t *ptr); -extern u64 atomic64_dec_return(atomic64_t *ptr); +static inline long long atomic64_sub_return(long long i, atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE(sub_return) + : "+A" (i), "+c" (v) + : : "memory" + ); + return i; +} + +static inline long long atomic64_inc_return(atomic64_t *v) +{ + long long a; + asm volatile(ATOMIC64_ALTERNATIVE(inc_return) + : "=A" (a) + : "S" (v) + : "memory", "ecx" + ); + return a; +} + +static inline long long atomic64_dec_return(atomic64_t *v) +{ + long long a; + asm volatile(ATOMIC64_ALTERNATIVE(dec_return) + : "=A" (a) + : "S" (v) + : "memory", "ecx" + ); + return a; +} /** * atomic64_add - add integer to atomic64 variable - * @delta: integer value to add - * @ptr: pointer to type atomic64_t + * @i: integer value to add + * @v: pointer to type atomic64_t * - * Atomically adds @delta to @ptr. + * Atomically adds @i to @v. */ -extern void atomic64_add(u64 delta, atomic64_t *ptr); +static inline long long atomic64_add(long long i, atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE_(add, add_return) + : "+A" (i), "+c" (v) + : : "memory" + ); + return i; +} /** * atomic64_sub - subtract the atomic64 variable - * @delta: integer value to subtract - * @ptr: pointer to type atomic64_t + * @i: integer value to subtract + * @v: pointer to type atomic64_t * - * Atomically subtracts @delta from @ptr. + * Atomically subtracts @i from @v. */ -extern void atomic64_sub(u64 delta, atomic64_t *ptr); +static inline long long atomic64_sub(long long i, atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE_(sub, sub_return) + : "+A" (i), "+c" (v) + : : "memory" + ); + return i; +} /** * atomic64_sub_and_test - subtract value from variable and test result - * @delta: integer value to subtract - * @ptr: pointer to type atomic64_t - * - * Atomically subtracts @delta from @ptr and returns + * @i: integer value to subtract + * @v: pointer to type atomic64_t + * + * Atomically subtracts @i from @v and returns * true if the result is zero, or false for all * other cases. */ -extern int atomic64_sub_and_test(u64 delta, atomic64_t *ptr); +static inline int atomic64_sub_and_test(long long i, atomic64_t *v) +{ + return atomic64_sub_return(i, v) == 0; +} /** * atomic64_inc - increment atomic64 variable - * @ptr: pointer to type atomic64_t + * @v: pointer to type atomic64_t * - * Atomically increments @ptr by 1. + * Atomically increments @v by 1. */ -extern void atomic64_inc(atomic64_t *ptr); +static inline void atomic64_inc(atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE_(inc, inc_return) + : : "S" (v) + : "memory", "eax", "ecx", "edx" + ); +} /** * atomic64_dec - decrement atomic64 variable @@ -124,37 +208,97 @@ extern void atomic64_inc(atomic64_t *ptr); * * Atomically decrements @ptr by 1. */ -extern void atomic64_dec(atomic64_t *ptr); +static inline void atomic64_dec(atomic64_t *v) +{ + asm volatile(ATOMIC64_ALTERNATIVE_(dec, dec_return) + : : "S" (v) + : "memory", "eax", "ecx", "edx" + ); +} /** * atomic64_dec_and_test - decrement and test - * @ptr: pointer to type atomic64_t + * @v: pointer to type atomic64_t * - * Atomically decrements @ptr by 1 and + * Atomically decrements @v by 1 and * returns true if the result is 0, or false for all other * cases. */ -extern int atomic64_dec_and_test(atomic64_t *ptr); +static inline int atomic64_dec_and_test(atomic64_t *v) +{ + return atomic64_dec_return(v) == 0; +} /** * atomic64_inc_and_test - increment and test - * @ptr: pointer to type atomic64_t + * @v: pointer to type atomic64_t * - * Atomically increments @ptr by 1 + * Atomically increments @v by 1 * and returns true if the result is zero, or false for all * other cases. */ -extern int atomic64_inc_and_test(atomic64_t *ptr); +static inline int atomic64_inc_and_test(atomic64_t *v) +{ + return atomic64_inc_return(v) == 0; +} /** * atomic64_add_negative - add and test if negative - * @delta: integer value to add - * @ptr: pointer to type atomic64_t + * @i: integer value to add + * @v: pointer to type atomic64_t * - * Atomically adds @delta to @ptr and returns true + * Atomically adds @i to @v and returns true * if the result is negative, or false when * result is greater than or equal to zero. */ -extern int atomic64_add_negative(u64 delta, atomic64_t *ptr); +static inline int atomic64_add_negative(long long i, atomic64_t *v) +{ + return atomic64_add_return(i, v) < 0; +} + +/** + * atomic64_add_unless - add unless the number is a given value + * @v: pointer of type atomic64_t + * @a: the amount to add to v... + * @u: ...unless v is equal to u. + * + * Atomically adds @a to @v, so long as it was not @u. + * Returns non-zero if @v was not @u, and zero otherwise. + */ +static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u) +{ + unsigned low = (unsigned)u; + unsigned high = (unsigned)(u >> 32); + asm volatile(ATOMIC64_ALTERNATIVE(add_unless) "\n\t" + : "+A" (a), "+c" (v), "+S" (low), "+D" (high) + : : "memory"); + return (int)a; +} + + +static inline int atomic64_inc_not_zero(atomic64_t *v) +{ + int r; + asm volatile(ATOMIC64_ALTERNATIVE(inc_not_zero) + : "=a" (r) + : "S" (v) + : "ecx", "edx", "memory" + ); + return r; +} + +static inline long long atomic64_dec_if_positive(atomic64_t *v) +{ + long long r; + asm volatile(ATOMIC64_ALTERNATIVE(dec_if_positive) + : "=A" (r) + : "S" (v) + : "ecx", "memory" + ); + return r; +} + +#undef ATOMIC64_ALTERNATIVE +#undef ATOMIC64_ALTERNATIVE_ #endif /* _ASM_X86_ATOMIC64_32_H */ -- cgit v1.2.1 From d7f6de1e9c4a12e11ba7186c70f0f40caa76f590 Mon Sep 17 00:00:00 2001 From: Luca Barbieri Date: Fri, 26 Feb 2010 12:22:41 +0100 Subject: x86: Implement atomic[64]_dec_if_positive() Add support for atomic_dec_if_positive(), and atomic64_dec_if_positive() for x86-64. atomic64_dec_if_positive() for x86-32 was already implemented in a previous patch. Signed-off-by: Luca Barbieri LKML-Reference: <1267183361-20775-2-git-send-email-luca@luca-barbieri.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/atomic.h | 23 +++++++++++++++++++++++ arch/x86/include/asm/atomic64_64.h | 23 +++++++++++++++++++++++ 2 files changed, 46 insertions(+) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h index 8f8217b9bdac..706c69492c14 100644 --- a/arch/x86/include/asm/atomic.h +++ b/arch/x86/include/asm/atomic.h @@ -246,6 +246,29 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u) #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0) +/* + * atomic_dec_if_positive - decrement by 1 if old value positive + * @v: pointer of type atomic_t + * + * The function returns the old value of *v minus 1, even if + * the atomic variable, v, was not decremented. + */ +static inline int atomic_dec_if_positive(atomic_t *v) +{ + int c, old, dec; + c = atomic_read(v); + for (;;) { + dec = c - 1; + if (unlikely(dec < 0)) + break; + old = atomic_cmpxchg((v), c, dec); + if (likely(old == c)) + break; + c = old; + } + return dec; +} + /** * atomic_inc_short - increment of a short integer * @v: pointer to type int diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h index 51c5b4056929..4d6e2cd6c88c 100644 --- a/arch/x86/include/asm/atomic64_64.h +++ b/arch/x86/include/asm/atomic64_64.h @@ -221,4 +221,27 @@ static inline int atomic64_add_unless(atomic64_t *v, long a, long u) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) +/* + * atomic64_dec_if_positive - decrement by 1 if old value positive + * @v: pointer of type atomic_t + * + * The function returns the old value of *v minus 1, even if + * the atomic variable, v, was not decremented. + */ +static inline long atomic64_dec_if_positive(atomic64_t *v) +{ + long c, old, dec; + c = atomic64_read(v); + for (;;) { + dec = c - 1; + if (unlikely(dec < 0)) + break; + old = atomic64_cmpxchg((v), c, dec); + if (likely(old == c)) + break; + c = old; + } + return dec; +} + #endif /* _ASM_X86_ATOMIC64_64_H */ -- cgit v1.2.1 From b701a47ba48b698976fb2fe05fb285b0edc1d26a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 29 Apr 2010 16:03:57 -0700 Subject: x86: Fix LOCK_PREFIX_HERE for uniprocessor build Checkin b3ac891b67bd4b1fc728d1c784cad1212dea433d: x86: Add support for lock prefix in alternatives ... did not define LOCK_PREFIX_HERE in the case of a uniprocessor build. As a result, it would cause any of the usages of this macro to fail on a uniprocessor build. Fix this by defining LOCK_PREFIX_HERE as a null string. Signed-off-by: H. Peter Anvin Cc: Luca Barbieri LKML-Reference: <1267005265-27958-2-git-send-email-luca@luca-barbieri.com> --- arch/x86/include/asm/alternative.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 55fee12cea6d..e29a6c9bba00 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -38,6 +38,7 @@ #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " #else /* ! CONFIG_SMP */ +#define LOCK_PREFIX_HERE "" #define LOCK_PREFIX "" #endif -- cgit v1.2.1