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1bc2c49539
Windows supports futex-like APIs since Windows 8 and Windows Server 2012. Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> Link: https://lore.kernel.org/r/20250529-event-v5-2-53b285203794@daynix.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/*
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* Wrappers around Linux futex syscall and similar
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*
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* Copyright Red Hat, Inc. 2017
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*
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* Author:
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* Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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/*
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* Note that a wake-up can also be caused by common futex usage patterns in
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* unrelated code that happened to have previously used the futex word's
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* memory location (e.g., typical futex-based implementations of Pthreads
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* mutexes can cause this under some conditions). Therefore, qemu_futex_wait()
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* callers should always conservatively assume that it is a spurious wake-up,
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* and use the futex word's value (i.e., the user-space synchronization scheme)
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* to decide whether to continue to block or not.
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*/
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#ifndef QEMU_FUTEX_H
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#define QEMU_FUTEX_H
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#define HAVE_FUTEX
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#ifdef CONFIG_LINUX
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#include <sys/syscall.h>
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#include <linux/futex.h>
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#define qemu_futex(...) syscall(__NR_futex, __VA_ARGS__)
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static inline void qemu_futex_wake_all(void *f)
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{
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qemu_futex(f, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
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}
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static inline void qemu_futex_wake_single(void *f)
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{
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qemu_futex(f, FUTEX_WAKE, 1, NULL, NULL, 0);
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}
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static inline void qemu_futex_wait(void *f, unsigned val)
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{
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while (qemu_futex(f, FUTEX_WAIT, (int) val, NULL, NULL, 0)) {
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switch (errno) {
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case EWOULDBLOCK:
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return;
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case EINTR:
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break; /* get out of switch and retry */
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default:
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abort();
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}
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}
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}
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#elif defined(CONFIG_WIN32)
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#include <synchapi.h>
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static inline void qemu_futex_wake_all(void *f)
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{
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WakeByAddressAll(f);
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}
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static inline void qemu_futex_wake_single(void *f)
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{
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WakeByAddressSingle(f);
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}
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static inline void qemu_futex_wait(void *f, unsigned val)
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{
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WaitOnAddress(f, &val, sizeof(val), INFINITE);
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}
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#else
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#undef HAVE_FUTEX
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#endif
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#endif /* QEMU_FUTEX_H */
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