diff --git a/MAINTAINERS b/MAINTAINERS index bf62247872..c21d6a2f9e 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3061,8 +3061,10 @@ S: Maintained F: docs/devel/lockcnt.rst F: docs/devel/rcu.rst F: include/qemu/rcu*.h +F: include/qemu/lockcnt.h F: tests/unit/rcutorture.c F: tests/unit/test-rcu-*.c +F: util/lockcnt.c F: util/rcu.c Human Monitor (HMP) diff --git a/accel/accel-blocker.c b/accel/accel-blocker.c index e083f24aa8..75daaa2911 100644 --- a/accel/accel-blocker.c +++ b/accel/accel-blocker.c @@ -25,6 +25,7 @@ */ #include "qemu/osdep.h" +#include "qemu/lockcnt.h" #include "qemu/thread.h" #include "qemu/main-loop.h" #include "hw/core/cpu.h" diff --git a/docs/devel/lockcnt.rst b/docs/devel/lockcnt.rst index 994aeb5715..728594bcea 100644 --- a/docs/devel/lockcnt.rst +++ b/docs/devel/lockcnt.rst @@ -175,7 +175,7 @@ three instructions in the critical path, two assignments and a ``smp_wmb()``. ``QemuLockCnt`` API ------------------- -The ``QemuLockCnt`` API is described in ``include/qemu/thread.h``. +The ``QemuLockCnt`` API is described in ``include/qemu/lockcnt.h``. ``QemuLockCnt`` usage diff --git a/hw/core/cpu-common.c b/hw/core/cpu-common.c index 7982ecd39a..09c7903594 100644 --- a/hw/core/cpu-common.c +++ b/hw/core/cpu-common.c @@ -24,6 +24,7 @@ #include "sysemu/hw_accel.h" #include "qemu/log.h" #include "qemu/main-loop.h" +#include "qemu/lockcnt.h" #include "exec/log.h" #include "exec/gdbstub.h" #include "sysemu/tcg.h" diff --git a/include/block/aio.h b/include/block/aio.h index 4ee81936ed..43883a8a33 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -20,6 +20,7 @@ #include "qemu/coroutine-core.h" #include "qemu/queue.h" #include "qemu/event_notifier.h" +#include "qemu/lockcnt.h" #include "qemu/thread.h" #include "qemu/timer.h" #include "block/graph-lock.h" diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h index d21a24c82f..c3ca0babcb 100644 --- a/include/hw/core/cpu.h +++ b/include/hw/core/cpu.h @@ -33,6 +33,7 @@ #include "qemu/bitmap.h" #include "qemu/rcu_queue.h" #include "qemu/queue.h" +#include "qemu/lockcnt.h" #include "qemu/thread.h" #include "qom/object.h" diff --git a/include/qemu/lockcnt.h b/include/qemu/lockcnt.h new file mode 100644 index 0000000000..2c92ae17c9 --- /dev/null +++ b/include/qemu/lockcnt.h @@ -0,0 +1,130 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * QemuLockCnt implementation + * + * Copyright Red Hat, Inc. 2017 + * + * Author: + * Paolo Bonzini + * + */ + +#ifndef QEMU_LOCKCNT_H +#define QEMU_LOCKCNT_H + +#include "qemu/thread.h" + +typedef struct QemuLockCnt QemuLockCnt; + +struct QemuLockCnt { +#ifndef CONFIG_LINUX + QemuMutex mutex; +#endif + unsigned count; +}; + +/** + * qemu_lockcnt_init: initialize a QemuLockcnt + * @lockcnt: the lockcnt to initialize + * + * Initialize lockcnt's counter to zero and prepare its mutex + * for usage. + */ +void qemu_lockcnt_init(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_destroy: destroy a QemuLockcnt + * @lockcnt: the lockcnt to destruct + * + * Destroy lockcnt's mutex. + */ +void qemu_lockcnt_destroy(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_inc: increment a QemuLockCnt's counter + * @lockcnt: the lockcnt to operate on + * + * If the lockcnt's count is zero, wait for critical sections + * to finish and increment lockcnt's count to 1. If the count + * is not zero, just increment it. + * + * Because this function can wait on the mutex, it must not be + * called while the lockcnt's mutex is held by the current thread. + * For the same reason, qemu_lockcnt_inc can also contribute to + * AB-BA deadlocks. This is a sample deadlock scenario: + * + * thread 1 thread 2 + * ------------------------------------------------------- + * qemu_lockcnt_lock(&lc1); + * qemu_lockcnt_lock(&lc2); + * qemu_lockcnt_inc(&lc2); + * qemu_lockcnt_inc(&lc1); + */ +void qemu_lockcnt_inc(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_dec: decrement a QemuLockCnt's counter + * @lockcnt: the lockcnt to operate on + */ +void qemu_lockcnt_dec(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_dec_and_lock: decrement a QemuLockCnt's counter and + * possibly lock it. + * @lockcnt: the lockcnt to operate on + * + * Decrement lockcnt's count. If the new count is zero, lock + * the mutex and return true. Otherwise, return false. + */ +bool qemu_lockcnt_dec_and_lock(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_dec_if_lock: possibly decrement a QemuLockCnt's counter and + * lock it. + * @lockcnt: the lockcnt to operate on + * + * If the count is 1, decrement the count to zero, lock + * the mutex and return true. Otherwise, return false. + */ +bool qemu_lockcnt_dec_if_lock(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_lock: lock a QemuLockCnt's mutex. + * @lockcnt: the lockcnt to operate on + * + * Remember that concurrent visits are not blocked unless the count is + * also zero. You can use qemu_lockcnt_count to check for this inside a + * critical section. + */ +void qemu_lockcnt_lock(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_unlock: release a QemuLockCnt's mutex. + * @lockcnt: the lockcnt to operate on. + */ +void qemu_lockcnt_unlock(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_inc_and_unlock: combined unlock/increment on a QemuLockCnt. + * @lockcnt: the lockcnt to operate on. + * + * This is the same as + * + * qemu_lockcnt_unlock(lockcnt); + * qemu_lockcnt_inc(lockcnt); + * + * but more efficient. + */ +void qemu_lockcnt_inc_and_unlock(QemuLockCnt *lockcnt); + +/** + * qemu_lockcnt_count: query a LockCnt's count. + * @lockcnt: the lockcnt to query. + * + * Note that the count can change at any time. Still, while the + * lockcnt is locked, one can usefully check whether the count + * is non-zero. + */ +unsigned qemu_lockcnt_count(QemuLockCnt *lockcnt); + +#endif diff --git a/include/qemu/thread.h b/include/qemu/thread.h index fb74e21c08..7eba27a704 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -293,115 +293,4 @@ static inline void qemu_spin_unlock(QemuSpin *spin) #endif } -struct QemuLockCnt { -#ifndef CONFIG_LINUX - QemuMutex mutex; -#endif - unsigned count; -}; - -/** - * qemu_lockcnt_init: initialize a QemuLockcnt - * @lockcnt: the lockcnt to initialize - * - * Initialize lockcnt's counter to zero and prepare its mutex - * for usage. - */ -void qemu_lockcnt_init(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_destroy: destroy a QemuLockcnt - * @lockcnt: the lockcnt to destruct - * - * Destroy lockcnt's mutex. - */ -void qemu_lockcnt_destroy(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_inc: increment a QemuLockCnt's counter - * @lockcnt: the lockcnt to operate on - * - * If the lockcnt's count is zero, wait for critical sections - * to finish and increment lockcnt's count to 1. If the count - * is not zero, just increment it. - * - * Because this function can wait on the mutex, it must not be - * called while the lockcnt's mutex is held by the current thread. - * For the same reason, qemu_lockcnt_inc can also contribute to - * AB-BA deadlocks. This is a sample deadlock scenario: - * - * thread 1 thread 2 - * ------------------------------------------------------- - * qemu_lockcnt_lock(&lc1); - * qemu_lockcnt_lock(&lc2); - * qemu_lockcnt_inc(&lc2); - * qemu_lockcnt_inc(&lc1); - */ -void qemu_lockcnt_inc(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_dec: decrement a QemuLockCnt's counter - * @lockcnt: the lockcnt to operate on - */ -void qemu_lockcnt_dec(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_dec_and_lock: decrement a QemuLockCnt's counter and - * possibly lock it. - * @lockcnt: the lockcnt to operate on - * - * Decrement lockcnt's count. If the new count is zero, lock - * the mutex and return true. Otherwise, return false. - */ -bool qemu_lockcnt_dec_and_lock(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_dec_if_lock: possibly decrement a QemuLockCnt's counter and - * lock it. - * @lockcnt: the lockcnt to operate on - * - * If the count is 1, decrement the count to zero, lock - * the mutex and return true. Otherwise, return false. - */ -bool qemu_lockcnt_dec_if_lock(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_lock: lock a QemuLockCnt's mutex. - * @lockcnt: the lockcnt to operate on - * - * Remember that concurrent visits are not blocked unless the count is - * also zero. You can use qemu_lockcnt_count to check for this inside a - * critical section. - */ -void qemu_lockcnt_lock(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_unlock: release a QemuLockCnt's mutex. - * @lockcnt: the lockcnt to operate on. - */ -void qemu_lockcnt_unlock(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_inc_and_unlock: combined unlock/increment on a QemuLockCnt. - * @lockcnt: the lockcnt to operate on. - * - * This is the same as - * - * qemu_lockcnt_unlock(lockcnt); - * qemu_lockcnt_inc(lockcnt); - * - * but more efficient. - */ -void qemu_lockcnt_inc_and_unlock(QemuLockCnt *lockcnt); - -/** - * qemu_lockcnt_count: query a LockCnt's count. - * @lockcnt: the lockcnt to query. - * - * Note that the count can change at any time. Still, while the - * lockcnt is locked, one can usefully check whether the count - * is non-zero. - */ -unsigned qemu_lockcnt_count(QemuLockCnt *lockcnt); - #endif diff --git a/util/aio-posix.c b/util/aio-posix.c index 266c9dd35f..06bf9f456c 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -17,6 +17,7 @@ #include "block/block.h" #include "block/thread-pool.h" #include "qemu/main-loop.h" +#include "qemu/lockcnt.h" #include "qemu/rcu.h" #include "qemu/rcu_queue.h" #include "qemu/sockets.h" diff --git a/util/aio-win32.c b/util/aio-win32.c index d144f9391f..6583d5c5f3 100644 --- a/util/aio-win32.c +++ b/util/aio-win32.c @@ -18,6 +18,7 @@ #include "qemu/osdep.h" #include "block/block.h" #include "qemu/main-loop.h" +#include "qemu/lockcnt.h" #include "qemu/queue.h" #include "qemu/sockets.h" #include "qapi/error.h" diff --git a/util/async.c b/util/async.c index 3e3e4fc712..99db28389f 100644 --- a/util/async.c +++ b/util/async.c @@ -30,6 +30,7 @@ #include "block/graph-lock.h" #include "qemu/main-loop.h" #include "qemu/atomic.h" +#include "qemu/lockcnt.h" #include "qemu/rcu_queue.h" #include "block/raw-aio.h" #include "qemu/coroutine_int.h" diff --git a/util/fdmon-epoll.c b/util/fdmon-epoll.c index c6413cb18f..9fb8800dde 100644 --- a/util/fdmon-epoll.c +++ b/util/fdmon-epoll.c @@ -5,6 +5,7 @@ #include "qemu/osdep.h" #include +#include "qemu/lockcnt.h" #include "qemu/rcu_queue.h" #include "aio-posix.h" diff --git a/util/lockcnt.c b/util/lockcnt.c index 5da36946b1..d07c6cc5ce 100644 --- a/util/lockcnt.c +++ b/util/lockcnt.c @@ -7,6 +7,7 @@ * Paolo Bonzini */ #include "qemu/osdep.h" +#include "qemu/lockcnt.h" #include "qemu/thread.h" #include "qemu/atomic.h" #include "trace.h"