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Wed, 28 May 2025 22:46:06 -0700 (PDT) From: Akihiko Odaki Date: Thu, 29 May 2025 14:45:51 +0900 Subject: [PATCH v5 02/13] futex: Support Windows MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250529-event-v5-2-53b285203794@daynix.com> References: <20250529-event-v5-0-53b285203794@daynix.com> In-Reply-To: <20250529-event-v5-0-53b285203794@daynix.com> To: Paolo Bonzini , Stefan Weil , Peter Xu , Fabiano Rosas , Hailiang Zhang Cc: Phil Dennis-Jordan , qemu-devel@nongnu.org, devel@daynix.com, =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Akihiko Odaki X-Mailer: b4 0.15-dev-edae6 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::42d; envelope-from=akihiko.odaki@daynix.com; helo=mail-pf1-x42d.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @daynix-com.20230601.gappssmtp.com) X-ZM-MESSAGEID: 1748497661509116600 Windows supports futex-like APIs since Windows 8 and Windows Server 2012. Signed-off-by: Akihiko Odaki --- meson.build | 2 ++ include/qemu/futex.h | 53 ++++++++++++++++++++++++++++++-----= ---- tests/unit/test-aio-multithread.c | 2 +- util/lockcnt.c | 2 +- util/qemu-thread-posix.c | 4 +-- util/meson.build | 2 +- 6 files changed, 48 insertions(+), 17 deletions(-) diff --git a/meson.build b/meson.build index ad2053f968b8..d865a2ff778e 100644 --- a/meson.build +++ b/meson.build @@ -837,11 +837,13 @@ emulator_link_args =3D [] midl =3D not_found widl =3D not_found pathcch =3D not_found +synchronization =3D not_found host_dsosuf =3D '.so' if host_os =3D=3D 'windows' midl =3D find_program('midl', required: false) widl =3D find_program('widl', required: false) pathcch =3D cc.find_library('pathcch') + synchronization =3D cc.find_library('Synchronization') socket =3D cc.find_library('ws2_32') winmm =3D cc.find_library('winmm') =20 diff --git a/include/qemu/futex.h b/include/qemu/futex.h index f57774005330..607613eec835 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 * @@ -11,28 +11,37 @@ * */ =20 +/* + * 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_w= ait() + * 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 sc= heme) + * to decide whether to continue to block or not. + */ + #ifndef QEMU_FUTEX_H #define QEMU_FUTEX_H =20 +#define HAVE_FUTEX + +#ifdef CONFIG_LINUX #include #include =20 #define qemu_futex(...) syscall(__NR_futex, __VA_ARGS__) =20 -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); } =20 -/* - * 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, callers shou= ld - * 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 wh= ether - * to continue to block or not. - */ static inline void qemu_futex_wait(void *f, unsigned val) { while (qemu_futex(f, FUTEX_WAIT, (int) val, NULL, NULL, 0)) { @@ -46,5 +55,25 @@ static inline void qemu_futex_wait(void *f, unsigned val) } } } +#elif defined(CONFIG_WIN32) +#include + +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 =20 #endif /* QEMU_FUTEX_H */ diff --git a/tests/unit/test-aio-multithread.c b/tests/unit/test-aio-multit= hread.c index 8c2e41545a29..0ead6bf34ad1 100644 --- a/tests/unit/test-aio-multithread.c +++ b/tests/unit/test-aio-multithread.c @@ -330,7 +330,7 @@ static void mcs_mutex_unlock(void) /* Wake up the next in line. */ next =3D qatomic_read(&nodes[id].next); nodes[next].locked =3D 0; - qemu_futex_wake(&nodes[next].locked, 1); + qemu_futex_wake_single(&nodes[next].locked); } =20 static void test_multi_fair_mutex_entry(void *opaque) diff --git a/util/lockcnt.c b/util/lockcnt.c index d07c6cc5cee4..ca27d8e61a5c 100644 --- a/util/lockcnt.c +++ b/util/lockcnt.c @@ -106,7 +106,7 @@ static bool qemu_lockcnt_cmpxchg_or_wait(QemuLockCnt *l= ockcnt, int *val, static void lockcnt_wake(QemuLockCnt *lockcnt) { trace_lockcnt_futex_wake(lockcnt); - qemu_futex_wake(&lockcnt->count, 1); + qemu_futex_wake_single(&lockcnt->count); } =20 void qemu_lockcnt_inc(QemuLockCnt *lockcnt) diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index 04fc3bf2298e..4d6f24d705c7 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -345,7 +345,7 @@ static inline void qemu_futex_wait(QemuEvent *ev, unsig= ned val) =20 /* Valid transitions: * - free->set, when setting the event - * - busy->set, when setting the event, followed by qemu_futex_wake + * - busy->set, when setting the event, followed by qemu_futex_wake_all * - set->free, when resetting the event * - free->busy, when waiting * @@ -396,7 +396,7 @@ void qemu_event_set(QemuEvent *ev) if (qatomic_read(&ev->value) !=3D EV_SET) { if (qatomic_xchg(&ev->value, EV_SET) =3D=3D EV_BUSY) { /* There were waiters, wake them up. */ - qemu_futex_wake(ev, INT_MAX); + qemu_futex_wake_all(ev); } } } diff --git a/util/meson.build b/util/meson.build index 1adff96ebd51..5735f65f1994 100644 --- a/util/meson.build +++ b/util/meson.build @@ -27,7 +27,7 @@ else util_ss.add(files('event_notifier-win32.c')) util_ss.add(files('oslib-win32.c')) util_ss.add(files('qemu-thread-win32.c')) - util_ss.add(winmm, pathcch) + util_ss.add(winmm, pathcch, synchronization) endif util_ss.add(when: linux_io_uring, if_true: files('fdmon-io_uring.c')) if glib_has_gslice --=20 2.49.0