Introduce an *_dec_not_zero operation. Make this a special case of *_add_unless because batman-adv uses atomic_dec_not_zero in different places like re-broadcast queue or aggregation queue management. There are other non-final patches which may also want to use this macro. Reported-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxx> Cc: Richard Henderson <rth@xxxxxxxxxxx> Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx> Cc: Matt Turner <mattst88@xxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> Cc: Hirokazu Takata <takata@xxxxxxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Kyle McMartin <kyle@xxxxxxxxxxx> Cc: Helge Deller <deller@xxxxxx> Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: linux390@xxxxxxxxxx Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx> Cc: Jeff Dike <jdike@xxxxxxxxxxx> Cc: Richard Weinberger <richard@xxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: linux-doc@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-alpha@xxxxxxxxxxxxxxx Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-ia64@xxxxxxxxxxxxxxx Cc: linux-m32r@xxxxxxxxxxxxxxxxx Cc: linux-m32r-ja@xxxxxxxxxxxxxxxxx Cc: linux-mips@xxxxxxxxxxxxxx Cc: linux-parisc@xxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-s390@xxxxxxxxxxxxxxx Cc: sparclinux@xxxxxxxxxxxxxxx Cc: user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx --- David S. Miller recommended this change in https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2011-May/004560.html Arnd Bergmann wanted to apply it in 201106172320.26476.arnd@xxxxxxxx ... and then Arun Sharma created a big merge conflict with https://lkml.org/lkml/2011/6/6/430 I don't think that it is a a good idea to asume that everyone still agrees with the patch after I've rewritten it. Documentation/atomic_ops.txt | 1 + arch/alpha/include/asm/atomic.h | 1 + arch/alpha/include/asm/local.h | 1 + arch/arm/include/asm/atomic.h | 1 + arch/ia64/include/asm/atomic.h | 1 + arch/m32r/include/asm/local.h | 1 + arch/mips/include/asm/atomic.h | 1 + arch/mips/include/asm/local.h | 1 + arch/parisc/include/asm/atomic.h | 1 + arch/powerpc/include/asm/atomic.h | 1 + arch/powerpc/include/asm/local.h | 1 + arch/s390/include/asm/atomic.h | 1 + arch/sparc/include/asm/atomic_64.h | 1 + arch/tile/include/asm/atomic_32.h | 1 + arch/tile/include/asm/atomic_64.h | 1 + arch/um/sys-i386/atomic64_cx8_32.S | 28 ++++++++++++++++++++++++++++ arch/x86/include/asm/atomic64_32.h | 12 ++++++++++++ arch/x86/include/asm/atomic64_64.h | 1 + arch/x86/include/asm/local.h | 1 + arch/x86/lib/atomic64_32.c | 4 ++++ arch/x86/lib/atomic64_386_32.S | 21 +++++++++++++++++++++ arch/x86/lib/atomic64_cx8_32.S | 28 ++++++++++++++++++++++++++++ include/asm-generic/atomic-long.h | 2 ++ include/asm-generic/atomic64.h | 1 + include/asm-generic/local.h | 1 + include/asm-generic/local64.h | 2 ++ include/linux/atomic.h | 9 +++++++++ 27 files changed, 125 insertions(+), 0 deletions(-) diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index 3bd585b..1eec221 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -190,6 +190,7 @@ atomic_add_unless requires explicit memory barriers around the operation unless it fails (returns 0). atomic_inc_not_zero, equivalent to atomic_add_unless(v, 1, 0) +atomic_dec_not_zero, equivalent to atomic_add_unless(v, -1, 0) If a caller requires memory barrier semantics around an atomic_t diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h index 640f909..09d1571 100644 --- a/arch/alpha/include/asm/atomic.h +++ b/arch/alpha/include/asm/atomic.h @@ -225,6 +225,7 @@ 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) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0) #define atomic64_add_negative(a, v) (atomic64_add_return((a), (v)) < 0) diff --git a/arch/alpha/include/asm/local.h b/arch/alpha/include/asm/local.h index 9c94b84..51eb678 100644 --- a/arch/alpha/include/asm/local.h +++ b/arch/alpha/include/asm/local.h @@ -79,6 +79,7 @@ static __inline__ long local_sub_return(long i, local_t * l) c != (u); \ }) #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_dec_not_zero(l) local_add_unless((l), -1, 0) #define local_add_negative(a, l) (local_add_return((a), (l)) < 0) diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h index 86976d0..80ed975 100644 --- a/arch/arm/include/asm/atomic.h +++ b/arch/arm/include/asm/atomic.h @@ -458,6 +458,7 @@ static inline int atomic64_add_unless(atomic64_t *v, u64 a, u64 u) #define atomic64_dec_return(v) atomic64_sub_return(1LL, (v)) #define atomic64_dec_and_test(v) (atomic64_dec_return((v)) == 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1LL, 0LL) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1LL, 0LL) #endif /* !CONFIG_GENERIC_ATOMIC64 */ #endif diff --git a/arch/ia64/include/asm/atomic.h b/arch/ia64/include/asm/atomic.h index 3fad89e..af6e9b2 100644 --- a/arch/ia64/include/asm/atomic.h +++ b/arch/ia64/include/asm/atomic.h @@ -122,6 +122,7 @@ static __inline__ long atomic64_add_unless(atomic64_t *v, long a, long u) } #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #define atomic_add_return(i,v) \ ({ \ diff --git a/arch/m32r/include/asm/local.h b/arch/m32r/include/asm/local.h index 734bca8..d536082 100644 --- a/arch/m32r/include/asm/local.h +++ b/arch/m32r/include/asm/local.h @@ -272,6 +272,7 @@ static inline int local_add_unless(local_t *l, long a, long u) } #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_dec_not_zero(l) local_add_unless((l), -1, 0) static inline void local_clear_mask(unsigned long mask, local_t *addr) { diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h index 1d93f81..babb043 100644 --- a/arch/mips/include/asm/atomic.h +++ b/arch/mips/include/asm/atomic.h @@ -697,6 +697,7 @@ 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) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #define atomic64_dec_return(v) atomic64_sub_return(1, (v)) #define atomic64_inc_return(v) atomic64_add_return(1, (v)) diff --git a/arch/mips/include/asm/local.h b/arch/mips/include/asm/local.h index 94fde8d..0242256 100644 --- a/arch/mips/include/asm/local.h +++ b/arch/mips/include/asm/local.h @@ -137,6 +137,7 @@ static __inline__ long local_sub_return(long i, local_t * l) c != (u); \ }) #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_dec_not_zero(l) local_add_unless((l), -1, 0) #define local_dec_return(l) local_sub_return(1, (l)) #define local_inc_return(l) local_add_return(1, (l)) diff --git a/arch/parisc/include/asm/atomic.h b/arch/parisc/include/asm/atomic.h index b1dc71f..8a50234 100644 --- a/arch/parisc/include/asm/atomic.h +++ b/arch/parisc/include/asm/atomic.h @@ -334,6 +334,7 @@ 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) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #endif /* !CONFIG_64BIT */ diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h index e2a4c26..c0131a6 100644 --- a/arch/powerpc/include/asm/atomic.h +++ b/arch/powerpc/include/asm/atomic.h @@ -468,6 +468,7 @@ 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) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #endif /* __powerpc64__ */ diff --git a/arch/powerpc/include/asm/local.h b/arch/powerpc/include/asm/local.h index b8da913..d182e34 100644 --- a/arch/powerpc/include/asm/local.h +++ b/arch/powerpc/include/asm/local.h @@ -134,6 +134,7 @@ static __inline__ int local_add_unless(local_t *l, long a, long u) } #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_dec_not_zero(l) local_add_unless((l), -1, 0) #define local_sub_and_test(a, l) (local_sub_return((a), (l)) == 0) #define local_dec_and_test(l) (local_dec_return((l)) == 0) diff --git a/arch/s390/include/asm/atomic.h b/arch/s390/include/asm/atomic.h index 8517d2a..92e7d5d 100644 --- a/arch/s390/include/asm/atomic.h +++ b/arch/s390/include/asm/atomic.h @@ -325,6 +325,7 @@ static inline long long atomic64_dec_if_positive(atomic64_t *v) #define atomic64_dec_return(_v) atomic64_sub_return(1, _v) #define atomic64_dec_and_test(_v) (atomic64_sub_return(1, _v) == 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) #define smp_mb__before_atomic_dec() smp_mb() #define smp_mb__after_atomic_dec() smp_mb() diff --git a/arch/sparc/include/asm/atomic_64.h b/arch/sparc/include/asm/atomic_64.h index 9f421df..94cf160 100644 --- a/arch/sparc/include/asm/atomic_64.h +++ b/arch/sparc/include/asm/atomic_64.h @@ -106,6 +106,7 @@ static inline long atomic64_add_unless(atomic64_t *v, long a, long u) } #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) /* Atomic operations are already serializing */ #define smp_mb__before_atomic_dec() barrier() diff --git a/arch/tile/include/asm/atomic_32.h b/arch/tile/include/asm/atomic_32.h index c03349e..9cfafb3 100644 --- a/arch/tile/include/asm/atomic_32.h +++ b/arch/tile/include/asm/atomic_32.h @@ -233,6 +233,7 @@ static inline void atomic64_set(atomic64_t *v, u64 n) #define atomic64_dec_return(v) atomic64_sub_return(1LL, (v)) #define atomic64_dec_and_test(v) (atomic64_dec_return((v)) == 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1LL, 0LL) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1LL, 0LL) /* * We need to barrier before modifying the word, since the _atomic_xxx() diff --git a/arch/tile/include/asm/atomic_64.h b/arch/tile/include/asm/atomic_64.h index 27fe667..9c22f50 100644 --- a/arch/tile/include/asm/atomic_64.h +++ b/arch/tile/include/asm/atomic_64.h @@ -141,6 +141,7 @@ static inline long atomic64_add_unless(atomic64_t *v, long a, long u) #define atomic64_add_negative(i, v) (atomic64_add_return((i), (v)) < 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) /* Atomic dec and inc don't implement barrier, so provide them if needed. */ #define smp_mb__before_atomic_dec() smp_mb() diff --git a/arch/um/sys-i386/atomic64_cx8_32.S b/arch/um/sys-i386/atomic64_cx8_32.S index 1e901d3..a58a1d4 100644 --- a/arch/um/sys-i386/atomic64_cx8_32.S +++ b/arch/um/sys-i386/atomic64_cx8_32.S @@ -223,3 +223,31 @@ ENTRY(atomic64_inc_not_zero_cx8) jmp 3b CFI_ENDPROC ENDPROC(atomic64_inc_not_zero_cx8) + +ENTRY(atomic64_dec_not_zero_cx8) + CFI_STARTPROC + SAVE ebx + + read64 %esi +1: + testl %eax, %eax + je 4f +2: + movl %eax, %ebx + movl %edx, %ecx + subl $1, %ebx + sbbl $0, %ecx + LOCK_PREFIX + cmpxchg8b (%esi) + jne 1b + + movl $1, %eax +3: + RESTORE ebx + ret +4: + testl %edx, %edx + jne 2b + jmp 3b + CFI_ENDPROC +ENDPROC(atomic64_dec_not_zero_cx8) diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h index 24098aa..3cd4431 100644 --- a/arch/x86/include/asm/atomic64_32.h +++ b/arch/x86/include/asm/atomic64_32.h @@ -287,6 +287,18 @@ static inline int atomic64_inc_not_zero(atomic64_t *v) return r; } + +static inline int atomic64_dec_not_zero(atomic64_t *v) +{ + int r; + asm volatile(ATOMIC64_ALTERNATIVE(dec_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; diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h index 017594d..93c9d8b 100644 --- a/arch/x86/include/asm/atomic64_64.h +++ b/arch/x86/include/asm/atomic64_64.h @@ -220,6 +220,7 @@ 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) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1, 0) /* * atomic64_dec_if_positive - decrement by 1 if old value positive diff --git a/arch/x86/include/asm/local.h b/arch/x86/include/asm/local.h index 9cdae5d..2c8c92d 100644 --- a/arch/x86/include/asm/local.h +++ b/arch/x86/include/asm/local.h @@ -185,6 +185,7 @@ static inline long local_sub_return(long i, local_t *l) c != (u); \ }) #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_dec_not_zero(l) local_add_unless((l), -1, 0) /* On x86_32, these are no better than the atomic variants. * On x86-64 these are better than the atomic variants on SMP kernels diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c index 042f682..7da05c3 100644 --- a/arch/x86/lib/atomic64_32.c +++ b/arch/x86/lib/atomic64_32.c @@ -24,6 +24,8 @@ long long atomic64_dec_if_positive_cx8(atomic64_t *v); EXPORT_SYMBOL(atomic64_dec_if_positive_cx8); int atomic64_inc_not_zero_cx8(atomic64_t *v); EXPORT_SYMBOL(atomic64_inc_not_zero_cx8); +int atomic64_dec_not_zero_cx8(atomic64_t *v); +EXPORT_SYMBOL(atomic64_dec_not_zero_cx8); int atomic64_add_unless_cx8(atomic64_t *v, long long a, long long u); EXPORT_SYMBOL(atomic64_add_unless_cx8); @@ -54,6 +56,8 @@ long long atomic64_dec_if_positive_386(atomic64_t *v); EXPORT_SYMBOL(atomic64_dec_if_positive_386); int atomic64_inc_not_zero_386(atomic64_t *v); EXPORT_SYMBOL(atomic64_inc_not_zero_386); +int atomic64_dec_not_zero_386(atomic64_t *v); +EXPORT_SYMBOL(atomic64_dec_not_zero_386); int atomic64_add_unless_386(atomic64_t *v, long long a, long long u); EXPORT_SYMBOL(atomic64_add_unless_386); #endif diff --git a/arch/x86/lib/atomic64_386_32.S b/arch/x86/lib/atomic64_386_32.S index e8e7e0d..c78337b 100644 --- a/arch/x86/lib/atomic64_386_32.S +++ b/arch/x86/lib/atomic64_386_32.S @@ -181,6 +181,27 @@ ENDP #undef v #define v %esi +BEGIN(dec_not_zero) + movl (v), %eax + movl 4(v), %edx + testl %eax, %eax + je 3f +1: + subl $1, %eax + sbbl $0, %edx + movl %eax, (v) + movl %edx, 4(v) + movl $1, %eax +2: + RET +3: + testl %edx, %edx + jne 1b + jmp 2b +ENDP +#undef v + +#define v %esi BEGIN(dec_if_positive) movl (v), %eax movl 4(v), %edx diff --git a/arch/x86/lib/atomic64_cx8_32.S b/arch/x86/lib/atomic64_cx8_32.S index 391a083..989638c 100644 --- a/arch/x86/lib/atomic64_cx8_32.S +++ b/arch/x86/lib/atomic64_cx8_32.S @@ -220,3 +220,31 @@ ENTRY(atomic64_inc_not_zero_cx8) jmp 3b CFI_ENDPROC ENDPROC(atomic64_inc_not_zero_cx8) + +ENTRY(atomic64_dec_not_zero_cx8) + CFI_STARTPROC + SAVE ebx + + read64 %esi +1: + testl %eax, %eax + je 4f +2: + movl %eax, %ebx + movl %edx, %ecx + subl $1, %ebx + sbbl $0, %ecx + LOCK_PREFIX + cmpxchg8b (%esi) + jne 1b + + movl $1, %eax +3: + RESTORE ebx + ret +4: + testl %edx, %edx + jne 2b + jmp 3b + CFI_ENDPROC +ENDPROC(atomic64_dec_not_zero_cx8) diff --git a/include/asm-generic/atomic-long.h b/include/asm-generic/atomic-long.h index b7babf0..0fe75ab 100644 --- a/include/asm-generic/atomic-long.h +++ b/include/asm-generic/atomic-long.h @@ -130,6 +130,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u) } #define atomic_long_inc_not_zero(l) atomic64_inc_not_zero((atomic64_t *)(l)) +#define atomic_long_dec_not_zero(l) atomic64_dec_not_zero((atomic64_t *)(l)) #define atomic_long_cmpxchg(l, old, new) \ (atomic64_cmpxchg((atomic64_t *)(l), (old), (new))) @@ -247,6 +248,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u) } #define atomic_long_inc_not_zero(l) atomic_inc_not_zero((atomic_t *)(l)) +#define atomic_long_dec_not_zero(l) atomic_dec_not_zero((atomic_t *)(l)) #define atomic_long_cmpxchg(l, old, new) \ (atomic_cmpxchg((atomic_t *)(l), (old), (new))) diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h index b18ce4f..90ff9b1 100644 --- a/include/asm-generic/atomic64.h +++ b/include/asm-generic/atomic64.h @@ -38,5 +38,6 @@ extern int atomic64_add_unless(atomic64_t *v, long long a, long long u); #define atomic64_dec_return(v) atomic64_sub_return(1LL, (v)) #define atomic64_dec_and_test(v) (atomic64_dec_return((v)) == 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1LL, 0LL) +#define atomic64_dec_not_zero(v) atomic64_add_unless((v), -1LL, 0LL) #endif /* _ASM_GENERIC_ATOMIC64_H */ diff --git a/include/asm-generic/local.h b/include/asm-generic/local.h index 9ceb03b..fabf4f3 100644 --- a/include/asm-generic/local.h +++ b/include/asm-generic/local.h @@ -44,6 +44,7 @@ typedef struct #define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n)) #define local_add_unless(l, _a, u) atomic_long_add_unless((&(l)->a), (_a), (u)) #define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a) +#define local_dec_not_zero(l) atomic_long_dec_not_zero(&(l)->a) /* Non-atomic variants, ie. preemption disabled and won't be touched * in interrupt, etc. Some archs can optimize this case well. */ diff --git a/include/asm-generic/local64.h b/include/asm-generic/local64.h index 5980002..76acbe2 100644 --- a/include/asm-generic/local64.h +++ b/include/asm-generic/local64.h @@ -45,6 +45,7 @@ typedef struct { #define local64_xchg(l, n) local_xchg((&(l)->a), (n)) #define local64_add_unless(l, _a, u) local_add_unless((&(l)->a), (_a), (u)) #define local64_inc_not_zero(l) local_inc_not_zero(&(l)->a) +#define local64_dec_not_zero(l) local_dec_not_zero(&(l)->a) /* Non-atomic variants, ie. preemption disabled and won't be touched * in interrupt, etc. Some archs can optimize this case well. */ @@ -83,6 +84,7 @@ typedef struct { #define local64_xchg(l, n) atomic64_xchg((&(l)->a), (n)) #define local64_add_unless(l, _a, u) atomic64_add_unless((&(l)->a), (_a), (u)) #define local64_inc_not_zero(l) atomic64_inc_not_zero(&(l)->a) +#define local64_dec_not_zero(l) atomic64_dec_not_zero(&(l)->a) /* Non-atomic variants, ie. preemption disabled and won't be touched * in interrupt, etc. Some archs can optimize this case well. */ diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 42b77b5..ad2b750 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -27,6 +27,15 @@ 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_not_zero - decrement unless the number is zero + * @v: pointer of type atomic_t + * + * Atomically decrements @v by 1, so long as @v is non-zero. + * Returns non-zero if @v was non-zero, and zero otherwise. + */ +#define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0) + +/** * atomic_inc_not_zero_hint - increment if not null * @v: pointer of type atomic_t * @hint: probable value of the atomic before the increment -- 1.7.5.4
