From 0e862838f290147ea9c16db852d8d494b552d38d Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 24 Jun 2022 14:13:07 +0200 Subject: bitops: unify non-atomic bitops prototypes across architectures Currently, there is a mess with the prototypes of the non-atomic bitops across the different architectures: ret bool, int, unsigned long nr int, long, unsigned int, unsigned long addr volatile unsigned long *, volatile void * Thankfully, it doesn't provoke any bugs, but can sometimes make the compiler angry when it's not handy at all. Adjust all the prototypes to the following standard: ret bool retval can be only 0 or 1 nr unsigned long native; signed makes no sense addr volatile unsigned long * bitmaps are arrays of ulongs Next, some architectures don't define 'arch_' versions as they don't support instrumentation, others do. To make sure there is always the same set of callables present and to ease any potential future changes, make them all follow the rule: * architecture-specific files define only 'arch_' versions; * non-prefixed versions can be defined only in asm-generic files; and place the non-prefixed definitions into a new file in asm-generic to be included by non-instrumented architectures. Finally, add some static assertions in order to prevent people from making a mess in this room again. I also used the %__always_inline attribute consistently, so that they always get resolved to the actual operations. Suggested-by: Andy Shevchenko Signed-off-by: Alexander Lobakin Acked-by: Mark Rutland Reviewed-by: Yury Norov Reviewed-by: Andy Shevchenko Signed-off-by: Yury Norov --- include/linux/bitops.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 7aaed501f768..87087454a288 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -26,12 +26,29 @@ extern unsigned int __sw_hweight16(unsigned int w); extern unsigned int __sw_hweight32(unsigned int w); extern unsigned long __sw_hweight64(__u64 w); +#include + /* * Include this here because some architectures need generic_ffs/fls in * scope */ #include +/* Check that the bitops prototypes are sane */ +#define __check_bitop_pr(name) \ + static_assert(__same_type(arch_##name, generic_##name) && \ + __same_type(name, generic_##name)) + +__check_bitop_pr(__set_bit); +__check_bitop_pr(__clear_bit); +__check_bitop_pr(__change_bit); +__check_bitop_pr(__test_and_set_bit); +__check_bitop_pr(__test_and_clear_bit); +__check_bitop_pr(__test_and_change_bit); +__check_bitop_pr(test_bit); + +#undef __check_bitop_pr + static inline int get_bitmask_order(unsigned int count) { int order; -- cgit v1.2.3-59-g8ed1b From bb7379bfa680bd48b468e856475778db2ad866c1 Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 24 Jun 2022 14:13:08 +0200 Subject: bitops: define const_*() versions of the non-atomics Define const_*() variants of the non-atomic bitops to be used when the input arguments are compile-time constants, so that the compiler will be always able to resolve those to compile-time constants as well. Those are mostly direct aliases for generic_*() with one exception for const_test_bit(): the original one is declared atomic-safe and thus doesn't discard the `volatile` qualifier, so in order to let optimize code, define it separately disregarding the qualifier. Add them to the compile-time type checks as well just in case. Suggested-by: Marco Elver Signed-off-by: Alexander Lobakin Reviewed-by: Marco Elver Reviewed-by: Andy Shevchenko Signed-off-by: Yury Norov --- include/asm-generic/bitops/generic-non-atomic.h | 31 +++++++++++++++++++++++++ include/linux/bitops.h | 1 + 2 files changed, 32 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/asm-generic/bitops/generic-non-atomic.h b/include/asm-generic/bitops/generic-non-atomic.h index b85b8a2ac239..3d5ebd24652b 100644 --- a/include/asm-generic/bitops/generic-non-atomic.h +++ b/include/asm-generic/bitops/generic-non-atomic.h @@ -127,4 +127,35 @@ generic_test_bit(unsigned long nr, const volatile unsigned long *addr) return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1))); } +/* + * const_*() definitions provide good compile-time optimizations when + * the passed arguments can be resolved at compile time. + */ +#define const___set_bit generic___set_bit +#define const___clear_bit generic___clear_bit +#define const___change_bit generic___change_bit +#define const___test_and_set_bit generic___test_and_set_bit +#define const___test_and_clear_bit generic___test_and_clear_bit +#define const___test_and_change_bit generic___test_and_change_bit + +/** + * const_test_bit - Determine whether a bit is set + * @nr: bit number to test + * @addr: Address to start counting from + * + * A version of generic_test_bit() which discards the `volatile` qualifier to + * allow a compiler to optimize code harder. Non-atomic and to be called only + * for testing compile-time constants, e.g. by the corresponding macros, not + * directly from "regular" code. + */ +static __always_inline bool +const_test_bit(unsigned long nr, const volatile unsigned long *addr) +{ + const unsigned long *p = (const unsigned long *)addr + BIT_WORD(nr); + unsigned long mask = BIT_MASK(nr); + unsigned long val = *p; + + return !!(val & mask); +} + #endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */ diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 87087454a288..d393297287d5 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -37,6 +37,7 @@ extern unsigned long __sw_hweight64(__u64 w); /* Check that the bitops prototypes are sane */ #define __check_bitop_pr(name) \ static_assert(__same_type(arch_##name, generic_##name) && \ + __same_type(const_##name, generic_##name) && \ __same_type(name, generic_##name)) __check_bitop_pr(__set_bit); -- cgit v1.2.3-59-g8ed1b From e69eb9c460f128b71c6b995d75a05244e4b6cc3e Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 24 Jun 2022 14:13:09 +0200 Subject: bitops: wrap non-atomic bitops with a transparent macro In preparation for altering the non-atomic bitops with a macro, wrap them in a transparent definition. This requires prepending one more '_' to their names in order to be able to do that seamlessly. It is a simple change, given that all the non-prefixed definitions are now in asm-generic. sparc32 already has several triple-underscored functions, so I had to rename them ('___' -> 'sp32_'). Signed-off-by: Alexander Lobakin Reviewed-by: Marco Elver Reviewed-by: Andy Shevchenko Signed-off-by: Yury Norov --- arch/sparc/include/asm/bitops_32.h | 18 +++++++------- arch/sparc/lib/atomic32.c | 12 +++++----- .../asm-generic/bitops/instrumented-non-atomic.h | 28 +++++++++++----------- .../bitops/non-instrumented-non-atomic.h | 14 +++++------ include/linux/bitops.h | 18 +++++++++++++- tools/include/asm-generic/bitops/non-atomic.h | 24 +++++++++---------- tools/include/linux/bitops.h | 16 +++++++++++++ 7 files changed, 81 insertions(+), 49 deletions(-) (limited to 'include/linux/bitops.h') diff --git a/arch/sparc/include/asm/bitops_32.h b/arch/sparc/include/asm/bitops_32.h index 889afa9f990f..3448c191b484 100644 --- a/arch/sparc/include/asm/bitops_32.h +++ b/arch/sparc/include/asm/bitops_32.h @@ -19,9 +19,9 @@ #error only can be included directly #endif -unsigned long ___set_bit(unsigned long *addr, unsigned long mask); -unsigned long ___clear_bit(unsigned long *addr, unsigned long mask); -unsigned long ___change_bit(unsigned long *addr, unsigned long mask); +unsigned long sp32___set_bit(unsigned long *addr, unsigned long mask); +unsigned long sp32___clear_bit(unsigned long *addr, unsigned long mask); +unsigned long sp32___change_bit(unsigned long *addr, unsigned long mask); /* * Set bit 'nr' in 32-bit quantity at address 'addr' where bit '0' @@ -36,7 +36,7 @@ static inline int test_and_set_bit(unsigned long nr, volatile unsigned long *add ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - return ___set_bit(ADDR, mask) != 0; + return sp32___set_bit(ADDR, mask) != 0; } static inline void set_bit(unsigned long nr, volatile unsigned long *addr) @@ -46,7 +46,7 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *addr) ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - (void) ___set_bit(ADDR, mask); + (void) sp32___set_bit(ADDR, mask); } static inline int test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) @@ -56,7 +56,7 @@ static inline int test_and_clear_bit(unsigned long nr, volatile unsigned long *a ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - return ___clear_bit(ADDR, mask) != 0; + return sp32___clear_bit(ADDR, mask) != 0; } static inline void clear_bit(unsigned long nr, volatile unsigned long *addr) @@ -66,7 +66,7 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *addr) ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - (void) ___clear_bit(ADDR, mask); + (void) sp32___clear_bit(ADDR, mask); } static inline int test_and_change_bit(unsigned long nr, volatile unsigned long *addr) @@ -76,7 +76,7 @@ static inline int test_and_change_bit(unsigned long nr, volatile unsigned long * ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - return ___change_bit(ADDR, mask) != 0; + return sp32___change_bit(ADDR, mask) != 0; } static inline void change_bit(unsigned long nr, volatile unsigned long *addr) @@ -86,7 +86,7 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *addr) ADDR = ((unsigned long *) addr) + (nr >> 5); mask = 1 << (nr & 31); - (void) ___change_bit(ADDR, mask); + (void) sp32___change_bit(ADDR, mask); } #include diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c index 8b81d0f00c97..cf80d1ae352b 100644 --- a/arch/sparc/lib/atomic32.c +++ b/arch/sparc/lib/atomic32.c @@ -120,7 +120,7 @@ void arch_atomic_set(atomic_t *v, int i) } EXPORT_SYMBOL(arch_atomic_set); -unsigned long ___set_bit(unsigned long *addr, unsigned long mask) +unsigned long sp32___set_bit(unsigned long *addr, unsigned long mask) { unsigned long old, flags; @@ -131,9 +131,9 @@ unsigned long ___set_bit(unsigned long *addr, unsigned long mask) return old & mask; } -EXPORT_SYMBOL(___set_bit); +EXPORT_SYMBOL(sp32___set_bit); -unsigned long ___clear_bit(unsigned long *addr, unsigned long mask) +unsigned long sp32___clear_bit(unsigned long *addr, unsigned long mask) { unsigned long old, flags; @@ -144,9 +144,9 @@ unsigned long ___clear_bit(unsigned long *addr, unsigned long mask) return old & mask; } -EXPORT_SYMBOL(___clear_bit); +EXPORT_SYMBOL(sp32___clear_bit); -unsigned long ___change_bit(unsigned long *addr, unsigned long mask) +unsigned long sp32___change_bit(unsigned long *addr, unsigned long mask) { unsigned long old, flags; @@ -157,7 +157,7 @@ unsigned long ___change_bit(unsigned long *addr, unsigned long mask) return old & mask; } -EXPORT_SYMBOL(___change_bit); +EXPORT_SYMBOL(sp32___change_bit); unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new) { diff --git a/include/asm-generic/bitops/instrumented-non-atomic.h b/include/asm-generic/bitops/instrumented-non-atomic.h index b019f77ef21c..988a3bbfba34 100644 --- a/include/asm-generic/bitops/instrumented-non-atomic.h +++ b/include/asm-generic/bitops/instrumented-non-atomic.h @@ -14,7 +14,7 @@ #include /** - * __set_bit - Set a bit in memory + * ___set_bit - Set a bit in memory * @nr: the bit to set * @addr: the address to start counting from * @@ -23,14 +23,14 @@ * succeeds. */ static __always_inline void -__set_bit(unsigned long nr, volatile unsigned long *addr) +___set_bit(unsigned long nr, volatile unsigned long *addr) { instrument_write(addr + BIT_WORD(nr), sizeof(long)); arch___set_bit(nr, addr); } /** - * __clear_bit - Clears a bit in memory + * ___clear_bit - Clears a bit in memory * @nr: the bit to clear * @addr: the address to start counting from * @@ -39,14 +39,14 @@ __set_bit(unsigned long nr, volatile unsigned long *addr) * succeeds. */ static __always_inline void -__clear_bit(unsigned long nr, volatile unsigned long *addr) +___clear_bit(unsigned long nr, volatile unsigned long *addr) { instrument_write(addr + BIT_WORD(nr), sizeof(long)); arch___clear_bit(nr, addr); } /** - * __change_bit - Toggle a bit in memory + * ___change_bit - Toggle a bit in memory * @nr: the bit to change * @addr: the address to start counting from * @@ -55,7 +55,7 @@ __clear_bit(unsigned long nr, volatile unsigned long *addr) * succeeds. */ static __always_inline void -__change_bit(unsigned long nr, volatile unsigned long *addr) +___change_bit(unsigned long nr, volatile unsigned long *addr) { instrument_write(addr + BIT_WORD(nr), sizeof(long)); arch___change_bit(nr, addr); @@ -86,7 +86,7 @@ static __always_inline void __instrument_read_write_bitop(long nr, volatile unsi } /** - * __test_and_set_bit - Set a bit and return its old value + * ___test_and_set_bit - Set a bit and return its old value * @nr: Bit to set * @addr: Address to count from * @@ -94,14 +94,14 @@ static __always_inline void __instrument_read_write_bitop(long nr, volatile unsi * can appear to succeed but actually fail. */ static __always_inline bool -__test_and_set_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_set_bit(unsigned long nr, volatile unsigned long *addr) { __instrument_read_write_bitop(nr, addr); return arch___test_and_set_bit(nr, addr); } /** - * __test_and_clear_bit - Clear a bit and return its old value + * ___test_and_clear_bit - Clear a bit and return its old value * @nr: Bit to clear * @addr: Address to count from * @@ -109,14 +109,14 @@ __test_and_set_bit(unsigned long nr, volatile unsigned long *addr) * can appear to succeed but actually fail. */ static __always_inline bool -__test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) { __instrument_read_write_bitop(nr, addr); return arch___test_and_clear_bit(nr, addr); } /** - * __test_and_change_bit - Change a bit and return its old value + * ___test_and_change_bit - Change a bit and return its old value * @nr: Bit to change * @addr: Address to count from * @@ -124,19 +124,19 @@ __test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) * can appear to succeed but actually fail. */ static __always_inline bool -__test_and_change_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_change_bit(unsigned long nr, volatile unsigned long *addr) { __instrument_read_write_bitop(nr, addr); return arch___test_and_change_bit(nr, addr); } /** - * test_bit - Determine whether a bit is set + * _test_bit - Determine whether a bit is set * @nr: bit number to test * @addr: Address to start counting from */ static __always_inline bool -test_bit(unsigned long nr, const volatile unsigned long *addr) +_test_bit(unsigned long nr, const volatile unsigned long *addr) { instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long)); return arch_test_bit(nr, addr); diff --git a/include/asm-generic/bitops/non-instrumented-non-atomic.h b/include/asm-generic/bitops/non-instrumented-non-atomic.h index e0fd7bf72a56..bdb9b1ffaee9 100644 --- a/include/asm-generic/bitops/non-instrumented-non-atomic.h +++ b/include/asm-generic/bitops/non-instrumented-non-atomic.h @@ -3,14 +3,14 @@ #ifndef __ASM_GENERIC_BITOPS_NON_INSTRUMENTED_NON_ATOMIC_H #define __ASM_GENERIC_BITOPS_NON_INSTRUMENTED_NON_ATOMIC_H -#define __set_bit arch___set_bit -#define __clear_bit arch___clear_bit -#define __change_bit arch___change_bit +#define ___set_bit arch___set_bit +#define ___clear_bit arch___clear_bit +#define ___change_bit arch___change_bit -#define __test_and_set_bit arch___test_and_set_bit -#define __test_and_clear_bit arch___test_and_clear_bit -#define __test_and_change_bit arch___test_and_change_bit +#define ___test_and_set_bit arch___test_and_set_bit +#define ___test_and_clear_bit arch___test_and_clear_bit +#define ___test_and_change_bit arch___test_and_change_bit -#define test_bit arch_test_bit +#define _test_bit arch_test_bit #endif /* __ASM_GENERIC_BITOPS_NON_INSTRUMENTED_NON_ATOMIC_H */ diff --git a/include/linux/bitops.h b/include/linux/bitops.h index d393297287d5..3c3afbae1533 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -26,8 +26,24 @@ extern unsigned int __sw_hweight16(unsigned int w); extern unsigned int __sw_hweight32(unsigned int w); extern unsigned long __sw_hweight64(__u64 w); +/* + * Defined here because those may be needed by architecture-specific static + * inlines. + */ + #include +#define bitop(op, nr, addr) \ + op(nr, addr) + +#define __set_bit(nr, addr) bitop(___set_bit, nr, addr) +#define __clear_bit(nr, addr) bitop(___clear_bit, nr, addr) +#define __change_bit(nr, addr) bitop(___change_bit, nr, addr) +#define __test_and_set_bit(nr, addr) bitop(___test_and_set_bit, nr, addr) +#define __test_and_clear_bit(nr, addr) bitop(___test_and_clear_bit, nr, addr) +#define __test_and_change_bit(nr, addr) bitop(___test_and_change_bit, nr, addr) +#define test_bit(nr, addr) bitop(_test_bit, nr, addr) + /* * Include this here because some architectures need generic_ffs/fls in * scope @@ -38,7 +54,7 @@ extern unsigned long __sw_hweight64(__u64 w); #define __check_bitop_pr(name) \ static_assert(__same_type(arch_##name, generic_##name) && \ __same_type(const_##name, generic_##name) && \ - __same_type(name, generic_##name)) + __same_type(_##name, generic_##name)) __check_bitop_pr(__set_bit); __check_bitop_pr(__clear_bit); diff --git a/tools/include/asm-generic/bitops/non-atomic.h b/tools/include/asm-generic/bitops/non-atomic.h index e5e78e42e57b..0c472a833408 100644 --- a/tools/include/asm-generic/bitops/non-atomic.h +++ b/tools/include/asm-generic/bitops/non-atomic.h @@ -5,7 +5,7 @@ #include /** - * __set_bit - Set a bit in memory + * ___set_bit - Set a bit in memory * @nr: the bit to set * @addr: the address to start counting from * @@ -14,7 +14,7 @@ * may be that only one operation succeeds. */ static __always_inline void -__set_bit(unsigned long nr, volatile unsigned long *addr) +___set_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -23,7 +23,7 @@ __set_bit(unsigned long nr, volatile unsigned long *addr) } static __always_inline void -__clear_bit(unsigned long nr, volatile unsigned long *addr) +___clear_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -32,7 +32,7 @@ __clear_bit(unsigned long nr, volatile unsigned long *addr) } /** - * __change_bit - Toggle a bit in memory + * ___change_bit - Toggle a bit in memory * @nr: the bit to change * @addr: the address to start counting from * @@ -41,7 +41,7 @@ __clear_bit(unsigned long nr, volatile unsigned long *addr) * may be that only one operation succeeds. */ static __always_inline void -__change_bit(unsigned long nr, volatile unsigned long *addr) +___change_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -50,7 +50,7 @@ __change_bit(unsigned long nr, volatile unsigned long *addr) } /** - * __test_and_set_bit - Set a bit and return its old value + * ___test_and_set_bit - Set a bit and return its old value * @nr: Bit to set * @addr: Address to count from * @@ -59,7 +59,7 @@ __change_bit(unsigned long nr, volatile unsigned long *addr) * but actually fail. You must protect multiple accesses with a lock. */ static __always_inline bool -__test_and_set_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_set_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -70,7 +70,7 @@ __test_and_set_bit(unsigned long nr, volatile unsigned long *addr) } /** - * __test_and_clear_bit - Clear a bit and return its old value + * ___test_and_clear_bit - Clear a bit and return its old value * @nr: Bit to clear * @addr: Address to count from * @@ -79,7 +79,7 @@ __test_and_set_bit(unsigned long nr, volatile unsigned long *addr) * but actually fail. You must protect multiple accesses with a lock. */ static __always_inline bool -__test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -91,7 +91,7 @@ __test_and_clear_bit(unsigned long nr, volatile unsigned long *addr) /* WARNING: non atomic and it can be reordered! */ static __always_inline bool -__test_and_change_bit(unsigned long nr, volatile unsigned long *addr) +___test_and_change_bit(unsigned long nr, volatile unsigned long *addr) { unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); @@ -102,12 +102,12 @@ __test_and_change_bit(unsigned long nr, volatile unsigned long *addr) } /** - * test_bit - Determine whether a bit is set + * _test_bit - Determine whether a bit is set * @nr: bit number to test * @addr: Address to start counting from */ static __always_inline bool -test_bit(unsigned long nr, const volatile unsigned long *addr) +_test_bit(unsigned long nr, const volatile unsigned long *addr) { return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1))); } diff --git a/tools/include/linux/bitops.h b/tools/include/linux/bitops.h index 5fca38fe1ba8..f18683b95ea6 100644 --- a/tools/include/linux/bitops.h +++ b/tools/include/linux/bitops.h @@ -25,6 +25,22 @@ extern unsigned int __sw_hweight16(unsigned int w); extern unsigned int __sw_hweight32(unsigned int w); extern unsigned long __sw_hweight64(__u64 w); +/* + * Defined here because those may be needed by architecture-specific static + * inlines. + */ + +#define bitop(op, nr, addr) \ + op(nr, addr) + +#define __set_bit(nr, addr) bitop(___set_bit, nr, addr) +#define __clear_bit(nr, addr) bitop(___clear_bit, nr, addr) +#define __change_bit(nr, addr) bitop(___change_bit, nr, addr) +#define __test_and_set_bit(nr, addr) bitop(___test_and_set_bit, nr, addr) +#define __test_and_clear_bit(nr, addr) bitop(___test_and_clear_bit, nr, addr) +#define __test_and_change_bit(nr, addr) bitop(___test_and_change_bit, nr, addr) +#define test_bit(nr, addr) bitop(_test_bit, nr, addr) + /* * Include this here because some architectures need generic_ffs/fls in * scope -- cgit v1.2.3-59-g8ed1b From b03fc1173c0c2bb8fad61902a862985cecdc4b1b Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 24 Jun 2022 14:13:10 +0200 Subject: bitops: let optimize out non-atomic bitops on compile-time constants Currently, many architecture-specific non-atomic bitop implementations use inline asm or other hacks which are faster or more robust when working with "real" variables (i.e. fields from the structures etc.), but the compilers have no clue how to optimize them out when called on compile-time constants. That said, the following code: DECLARE_BITMAP(foo, BITS_PER_LONG) = { }; // -> unsigned long foo[1]; unsigned long bar = BIT(BAR_BIT); unsigned long baz = 0; __set_bit(FOO_BIT, foo); baz |= BIT(BAZ_BIT); BUILD_BUG_ON(!__builtin_constant_p(test_bit(FOO_BIT, foo)); BUILD_BUG_ON(!__builtin_constant_p(bar & BAR_BIT)); BUILD_BUG_ON(!__builtin_constant_p(baz & BAZ_BIT)); triggers the first assertion on x86_64, which means that the compiler is unable to evaluate it to a compile-time initializer when the architecture-specific bitop is used even if it's obvious. In order to let the compiler optimize out such cases, expand the bitop() macro to use the "constant" C non-atomic bitop implementations when all of the arguments passed are compile-time constants, which means that the result will be a compile-time constant as well, so that it produces more efficient and simple code in 100% cases, comparing to the architecture-specific counterparts. The savings are architecture, compiler and compiler flags dependent, for example, on x86_64 -O2: GCC 12: add/remove: 78/29 grow/shrink: 332/525 up/down: 31325/-61560 (-30235) LLVM 13: add/remove: 79/76 grow/shrink: 184/537 up/down: 55076/-141892 (-86816) LLVM 14: add/remove: 10/3 grow/shrink: 93/138 up/down: 3705/-6992 (-3287) and ARM64 (courtesy of Mark): GCC 11: add/remove: 92/29 grow/shrink: 933/2766 up/down: 39340/-82580 (-43240) LLVM 14: add/remove: 21/11 grow/shrink: 620/651 up/down: 12060/-15824 (-3764) Cc: Mark Rutland Signed-off-by: Alexander Lobakin Reviewed-by: Marco Elver Signed-off-by: Yury Norov --- include/linux/bitops.h | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 3c3afbae1533..cf9bf65039f2 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -33,8 +33,24 @@ extern unsigned long __sw_hweight64(__u64 w); #include +/* + * Many architecture-specific non-atomic bitops contain inline asm code and due + * to that the compiler can't optimize them to compile-time expressions or + * constants. In contrary, generic_*() helpers are defined in pure C and + * compilers optimize them just well. + * Therefore, to make `unsigned long foo = 0; __set_bit(BAR, &foo)` effectively + * equal to `unsigned long foo = BIT(BAR)`, pick the generic C alternative when + * the arguments can be resolved at compile time. That expression itself is a + * constant and doesn't bring any functional changes to the rest of cases. + * The casts to `uintptr_t` are needed to mitigate `-Waddress` warnings when + * passing a bitmap from .bss or .data (-> `!!addr` is always true). + */ #define bitop(op, nr, addr) \ - op(nr, addr) + ((__builtin_constant_p(nr) && \ + __builtin_constant_p((uintptr_t)(addr) != (uintptr_t)NULL) && \ + (uintptr_t)(addr) != (uintptr_t)NULL && \ + __builtin_constant_p(*(const unsigned long *)(addr))) ? \ + const##op(nr, addr) : op(nr, addr)) #define __set_bit(nr, addr) bitop(___set_bit, nr, addr) #define __clear_bit(nr, addr) bitop(___clear_bit, nr, addr) -- cgit v1.2.3-59-g8ed1b From 8238b4579866b7c1bb99883cfe102a43db5506ff Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 26 Aug 2022 09:17:08 -0400 Subject: wait_on_bit: add an acquire memory barrier There are several places in the kernel where wait_on_bit is not followed by a memory barrier (for example, in drivers/md/dm-bufio.c:new_read). On architectures with weak memory ordering, it may happen that memory accesses that follow wait_on_bit are reordered before wait_on_bit and they may return invalid data. Fix this class of bugs by introducing a new function "test_bit_acquire" that works like test_bit, but has acquire memory ordering semantics. Signed-off-by: Mikulas Patocka Acked-by: Will Deacon Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds --- Documentation/atomic_bitops.txt | 10 ++++------ arch/x86/include/asm/bitops.h | 21 +++++++++++++++++++++ include/asm-generic/bitops/generic-non-atomic.h | 14 ++++++++++++++ .../asm-generic/bitops/instrumented-non-atomic.h | 12 ++++++++++++ include/asm-generic/bitops/non-atomic.h | 1 + .../bitops/non-instrumented-non-atomic.h | 1 + include/linux/bitops.h | 1 + include/linux/buffer_head.h | 2 +- include/linux/wait_bit.h | 8 ++++---- kernel/sched/wait_bit.c | 2 +- 10 files changed, 60 insertions(+), 12 deletions(-) (limited to 'include/linux/bitops.h') diff --git a/Documentation/atomic_bitops.txt b/Documentation/atomic_bitops.txt index d8b101c97031..edea4656c5c0 100644 --- a/Documentation/atomic_bitops.txt +++ b/Documentation/atomic_bitops.txt @@ -58,13 +58,11 @@ Like with atomic_t, the rule of thumb is: - RMW operations that have a return value are fully ordered. - - RMW operations that are conditional are unordered on FAILURE, - otherwise the above rules apply. In the case of test_and_set_bit_lock(), - if the bit in memory is unchanged by the operation then it is deemed to have - failed. + - RMW operations that are conditional are fully ordered. -Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics and -clear_bit_unlock() which has RELEASE semantics. +Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics, +clear_bit_unlock() which has RELEASE semantics and test_bit_acquire which has +ACQUIRE semantics. Since a platform only has a single means of achieving atomic operations the same barriers as for atomic_t are used, see atomic_t.txt. diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index 973c6bd17f98..0fe9de58af31 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -207,6 +207,20 @@ static __always_inline bool constant_test_bit(long nr, const volatile unsigned l (addr[nr >> _BITOPS_LONG_SHIFT])) != 0; } +static __always_inline bool constant_test_bit_acquire(long nr, const volatile unsigned long *addr) +{ + bool oldbit; + + asm volatile("testb %2,%1" + CC_SET(nz) + : CC_OUT(nz) (oldbit) + : "m" (((unsigned char *)addr)[nr >> 3]), + "i" (1 << (nr & 7)) + :"memory"); + + return oldbit; +} + static __always_inline bool variable_test_bit(long nr, volatile const unsigned long *addr) { bool oldbit; @@ -226,6 +240,13 @@ arch_test_bit(unsigned long nr, const volatile unsigned long *addr) variable_test_bit(nr, addr); } +static __always_inline bool +arch_test_bit_acquire(unsigned long nr, const volatile unsigned long *addr) +{ + return __builtin_constant_p(nr) ? constant_test_bit_acquire(nr, addr) : + variable_test_bit(nr, addr); +} + /** * __ffs - find first set bit in word * @word: The word to search diff --git a/include/asm-generic/bitops/generic-non-atomic.h b/include/asm-generic/bitops/generic-non-atomic.h index 3d5ebd24652b..564a8c675d85 100644 --- a/include/asm-generic/bitops/generic-non-atomic.h +++ b/include/asm-generic/bitops/generic-non-atomic.h @@ -4,6 +4,7 @@ #define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H #include +#include #ifndef _LINUX_BITOPS_H #error only can be included directly @@ -127,6 +128,18 @@ generic_test_bit(unsigned long nr, const volatile unsigned long *addr) return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1))); } +/** + * generic_test_bit_acquire - Determine, with acquire semantics, whether a bit is set + * @nr: bit number to test + * @addr: Address to start counting from + */ +static __always_inline bool +generic_test_bit_acquire(unsigned long nr, const volatile unsigned long *addr) +{ + unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); + return 1UL & (smp_load_acquire(p) >> (nr & (BITS_PER_LONG-1))); +} + /* * const_*() definitions provide good compile-time optimizations when * the passed arguments can be resolved at compile time. @@ -137,6 +150,7 @@ generic_test_bit(unsigned long nr, const volatile unsigned long *addr) #define const___test_and_set_bit generic___test_and_set_bit #define const___test_and_clear_bit generic___test_and_clear_bit #define const___test_and_change_bit generic___test_and_change_bit +#define const_test_bit_acquire generic_test_bit_acquire /** * const_test_bit - Determine whether a bit is set diff --git a/include/asm-generic/bitops/instrumented-non-atomic.h b/include/asm-generic/bitops/instrumented-non-atomic.h index 988a3bbfba34..2b238b161a62 100644 --- a/include/asm-generic/bitops/instrumented-non-atomic.h +++ b/include/asm-generic/bitops/instrumented-non-atomic.h @@ -142,4 +142,16 @@ _test_bit(unsigned long nr, const volatile unsigned long *addr) return arch_test_bit(nr, addr); } +/** + * _test_bit_acquire - Determine, with acquire semantics, whether a bit is set + * @nr: bit number to test + * @addr: Address to start counting from + */ +static __always_inline bool +_test_bit_acquire(unsigned long nr, const volatile unsigned long *addr) +{ + instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long)); + return arch_test_bit_acquire(nr, addr); +} + #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */ diff --git a/include/asm-generic/bitops/non-atomic.h b/include/asm-generic/bitops/non-atomic.h index 5c37ced343ae..71f8d54a5195 100644 --- a/include/asm-generic/bitops/non-atomic.h +++ b/include/asm-generic/bitops/non-atomic.h @@ -13,6 +13,7 @@ #define arch___test_and_change_bit generic___test_and_change_bit #define arch_test_bit generic_test_bit +#define arch_test_bit_acquire generic_test_bit_acquire #include diff --git a/include/asm-generic/bitops/non-instrumented-non-atomic.h b/include/asm-generic/bitops/non-instrumented-non-atomic.h index bdb9b1ffaee9..0ddc78dfc358 100644 --- a/include/asm-generic/bitops/non-instrumented-non-atomic.h +++ b/include/asm-generic/bitops/non-instrumented-non-atomic.h @@ -12,5 +12,6 @@ #define ___test_and_change_bit arch___test_and_change_bit #define _test_bit arch_test_bit +#define _test_bit_acquire arch_test_bit_acquire #endif /* __ASM_GENERIC_BITOPS_NON_INSTRUMENTED_NON_ATOMIC_H */ diff --git a/include/linux/bitops.h b/include/linux/bitops.h index cf9bf65039f2..3b89c64bcfd8 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -59,6 +59,7 @@ extern unsigned long __sw_hweight64(__u64 w); #define __test_and_clear_bit(nr, addr) bitop(___test_and_clear_bit, nr, addr) #define __test_and_change_bit(nr, addr) bitop(___test_and_change_bit, nr, addr) #define test_bit(nr, addr) bitop(_test_bit, nr, addr) +#define test_bit_acquire(nr, addr) bitop(_test_bit_acquire, nr, addr) /* * Include this here because some architectures need generic_ffs/fls in diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index def8b8d30ccc..089c9ade4325 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -156,7 +156,7 @@ static __always_inline int buffer_uptodate(const struct buffer_head *bh) * make it consistent with folio_test_uptodate * pairs with smp_mb__before_atomic in set_buffer_uptodate */ - return (smp_load_acquire(&bh->b_state) & (1UL << BH_Uptodate)) != 0; + return test_bit_acquire(BH_Uptodate, &bh->b_state); } #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h index 7dec36aecbd9..7725b7579b78 100644 --- a/include/linux/wait_bit.h +++ b/include/linux/wait_bit.h @@ -71,7 +71,7 @@ static inline int wait_on_bit(unsigned long *word, int bit, unsigned mode) { might_sleep(); - if (!test_bit(bit, word)) + if (!test_bit_acquire(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, bit_wait, @@ -96,7 +96,7 @@ static inline int wait_on_bit_io(unsigned long *word, int bit, unsigned mode) { might_sleep(); - if (!test_bit(bit, word)) + if (!test_bit_acquire(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, bit_wait_io, @@ -123,7 +123,7 @@ wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode, unsigned long timeout) { might_sleep(); - if (!test_bit(bit, word)) + if (!test_bit_acquire(bit, word)) return 0; return out_of_line_wait_on_bit_timeout(word, bit, bit_wait_timeout, @@ -151,7 +151,7 @@ wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action, unsigned mode) { might_sleep(); - if (!test_bit(bit, word)) + if (!test_bit_acquire(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, action, mode); } diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c index d4788f810b55..0b1cd985dc27 100644 --- a/kernel/sched/wait_bit.c +++ b/kernel/sched/wait_bit.c @@ -47,7 +47,7 @@ __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_ prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode); if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) ret = (*action)(&wbq_entry->key, mode); - } while (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret); + } while (test_bit_acquire(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret); finish_wait(wq_head, &wbq_entry->wq_entry); -- cgit v1.2.3-59-g8ed1b