diff options
Diffstat (limited to 'include/qemu/futex.h')
| -rw-r--r-- | include/qemu/futex.h | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/include/qemu/futex.h b/include/qemu/futex.h index 91ae889..607613e 100644 --- a/include/qemu/futex.h +++ b/include/qemu/futex.h @@ -1,5 +1,5 @@ /* - * Wrappers around Linux futex syscall + * Wrappers around Linux futex syscall and similar * * Copyright Red Hat, Inc. 2017 * @@ -11,17 +11,35 @@ * */ +/* + * Note that a wake-up can also be caused by common futex usage patterns in + * unrelated code that happened to have previously used the futex word's + * memory location (e.g., typical futex-based implementations of Pthreads + * mutexes can cause this under some conditions). Therefore, qemu_futex_wait() + * callers should always conservatively assume that it is a spurious wake-up, + * and use the futex word's value (i.e., the user-space synchronization scheme) + * to decide whether to continue to block or not. + */ + #ifndef QEMU_FUTEX_H #define QEMU_FUTEX_H +#define HAVE_FUTEX + +#ifdef CONFIG_LINUX #include <sys/syscall.h> #include <linux/futex.h> #define qemu_futex(...) syscall(__NR_futex, __VA_ARGS__) -static inline void qemu_futex_wake(void *f, int n) +static inline void qemu_futex_wake_all(void *f) { - qemu_futex(f, FUTEX_WAKE, n, NULL, NULL, 0); + qemu_futex(f, FUTEX_WAKE, INT_MAX, NULL, NULL, 0); +} + +static inline void qemu_futex_wake_single(void *f) +{ + qemu_futex(f, FUTEX_WAKE, 1, NULL, NULL, 0); } static inline void qemu_futex_wait(void *f, unsigned val) @@ -37,5 +55,25 @@ static inline void qemu_futex_wait(void *f, unsigned val) } } } +#elif defined(CONFIG_WIN32) +#include <synchapi.h> + +static inline void qemu_futex_wake_all(void *f) +{ + WakeByAddressAll(f); +} + +static inline void qemu_futex_wake_single(void *f) +{ + WakeByAddressSingle(f); +} + +static inline void qemu_futex_wait(void *f, unsigned val) +{ + WaitOnAddress(f, &val, sizeof(val), INFINITE); +} +#else +#undef HAVE_FUTEX +#endif #endif /* QEMU_FUTEX_H */ |