Messages in this thread Patch in this message | | | From | Nikanth Karthikesan <> | Subject | [PATCH] Detect and warn on atomic_inc/atomic_dec wrapping around | Date | Thu, 30 Apr 2009 12:59:11 +0530 |
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Add a debug option to detect and warn when the 32-bit atomic_t wraps around during atomic_inc and atomic_dec.
Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
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diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h index 85b46fb..92b898f 100644 --- a/arch/x86/include/asm/atomic_32.h +++ b/arch/x86/include/asm/atomic_32.h @@ -3,8 +3,10 @@ #include <linux/compiler.h> #include <linux/types.h> +#include <linux/kernel.h> #include <asm/processor.h> #include <asm/cmpxchg.h> +#include <asm/bug.h> /* * Atomic operations that C can't guarantee us. Useful for @@ -77,6 +79,8 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) return c; } +static inline int atomic_add_unless(atomic_t *v, int a, int u); + /** * atomic_inc - increment atomic variable * @v: pointer of type atomic_t @@ -85,8 +89,12 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) */ static inline void atomic_inc(atomic_t *v) { +#if defined(CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP) + WARN_ON(atomic_add_unless(v, 1, INT_MAX) == 0); +#else asm volatile(LOCK_PREFIX "incl %0" : "+m" (v->counter)); +#endif } /** @@ -97,8 +105,12 @@ static inline void atomic_inc(atomic_t *v) */ static inline void atomic_dec(atomic_t *v) { +#if defined(CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP) + WARN_ON(atomic_add_unless(v, -1, INT_MIN) == 0); +#else asm volatile(LOCK_PREFIX "decl %0" : "+m" (v->counter)); +#endif } /** diff --git a/arch/x86/include/asm/atomic_64.h b/arch/x86/include/asm/atomic_64.h index 8c21731..c34a6fa 100644 --- a/arch/x86/include/asm/atomic_64.h +++ b/arch/x86/include/asm/atomic_64.h @@ -2,8 +2,10 @@ #define _ASM_X86_ATOMIC_64_H #include <linux/types.h> +#include <linux/kernel.h> #include <asm/alternative.h> #include <asm/cmpxchg.h> +#include <asm/bug.h> /* * Atomic operations that C can't guarantee us. Useful for @@ -76,6 +78,8 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) return c; } +static inline int atomic_add_unless(atomic_t *v, int a, int u); + /** * atomic_inc - increment atomic variable * @v: pointer of type atomic_t @@ -84,9 +88,13 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) */ static inline void atomic_inc(atomic_t *v) { +#if defined(CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP) + WARN_ON(atomic_add_unless(v, 1, INT_MAX) == 0); +#else asm volatile(LOCK_PREFIX "incl %0" : "=m" (v->counter) : "m" (v->counter)); +#endif } /** @@ -97,9 +105,13 @@ static inline void atomic_inc(atomic_t *v) */ static inline void atomic_dec(atomic_t *v) { +#if defined(CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP) + WARN_ON(atomic_add_unless(v, -1, INT_MIN) == 0); +#else asm volatile(LOCK_PREFIX "decl %0" : "=m" (v->counter) : "m" (v->counter)); +#endif } /** diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 812c282..a446a98 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -17,6 +17,13 @@ config ENABLE_WARN_DEPRECATED Disable this to suppress the "warning: 'foo' is deprecated (declared at kernel/power/somefile.c:1234)" messages. +config ENABLE_WARN_ATOMIC_INC_WRAP + bool "Enable warning on atomic_inc()/atomic_dec() wrap" + default y + help + Enable printing a warning when atomic_inc() or atomic_dec() + operation wraps around the 32-bit value. + config ENABLE_MUST_CHECK bool "Enable __must_check logic" default y
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