Make the x86 mutex implementation use ISO atomic ops rather than inline assembly.
Signed-off-by: David Howells <[email protected]> --- arch/x86/include/asm/mutex.h | 6 +-- arch/x86/include/asm/mutex_iso.h | 73 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 74 insertions(+), 5 deletions(-) create mode 100644 arch/x86/include/asm/mutex_iso.h diff --git a/arch/x86/include/asm/mutex.h b/arch/x86/include/asm/mutex.h index 7d3a48275394..831bc5a73886 100644 --- a/arch/x86/include/asm/mutex.h +++ b/arch/x86/include/asm/mutex.h @@ -1,5 +1 @@ -#ifdef CONFIG_X86_32 -# include <asm/mutex_32.h> -#else -# include <asm/mutex_64.h> -#endif +#include <asm/mutex_iso.h> diff --git a/arch/x86/include/asm/mutex_iso.h b/arch/x86/include/asm/mutex_iso.h new file mode 100644 index 000000000000..ffdbdb411989 --- /dev/null +++ b/arch/x86/include/asm/mutex_iso.h @@ -0,0 +1,73 @@ +/* ISO atomics based mutex + * + * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. + * Written by David Howells ([email protected]) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ +#ifndef _ASM_X86_MUTEX_ISO_H +#define _ASM_X86_MUTEX_ISO_H + +/** + * __mutex_fastpath_lock - decrement and call function if negative + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is negative + * + * Atomically decrements @v and calls <fail_fn> if the result is negative. + */ +static inline void __mutex_fastpath_lock(atomic_t *v, + void (*fail_fn)(atomic_t *)) +{ + if (atomic_dec_return_acquire(v) < 0) + fail_fn(v); +} + +/** + * __mutex_fastpath_lock_retval - try to take the lock by moving the count + * from 1 to a 0 value + * @v: pointer of type atomic_t + * + * Change the count from 1 to a value lower than 1. This function returns 0 + * if the fastpath succeeds, or -1 otherwise. + */ +static inline int __mutex_fastpath_lock_retval(atomic_t *v) +{ + return unlikely(atomic_dec_return(v) < 0) ? -1 : 0; +} + +/** + * __mutex_fastpath_unlock - increment and call function if nonpositive + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is nonpositive + * + * Atomically increments @v and calls <fail_fn> if the result is nonpositive. + */ +static inline void __mutex_fastpath_unlock(atomic_t *v, + void (*fail_fn)(atomic_t *)) +{ + if (atomic_inc_return_release(v) <= 0) + fail_fn(v); +} + +#define __mutex_slowpath_needs_to_unlock() 1 + +/** + * __mutex_fastpath_trylock - try to acquire the mutex, without waiting + * + * @v: pointer of type atomic_t + * @fail_fn: fallback function + * + * Change the count from 1 to 0 and return true (success), or return false + * (failure) if it wasn't 1 originally. [the fallback function is never used on + * x86_64, because all x86_64 CPUs have a CMPXCHG instruction.] + */ +static inline bool __mutex_fastpath_trylock(atomic_t *v, + int (*fail_fn)(atomic_t *)) +{ + return likely(atomic_try_cmpxchg(v, 1, 0)); +} + +#endif /* _ASM_X86_MUTEX_ISO_H */
