diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/Makefile.objs | 1 | ||||
| -rw-r--r-- | util/oslib-posix.c | 4 | ||||
| -rw-r--r-- | util/qemu-thread-posix.c | 2 | ||||
| -rw-r--r-- | util/rfifolock.c | 78 |
4 files changed, 84 insertions, 1 deletions
diff --git a/util/Makefile.objs b/util/Makefile.objs index 937376b082..df83b629a0 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -14,3 +14,4 @@ util-obj-y += crc32c.o util-obj-y += throttle.o util-obj-y += getauxval.o util-obj-y += readline.o +util-obj-y += rfifolock.o diff --git a/util/oslib-posix.c b/util/oslib-posix.c index c2eeb4fe40..8e9c770d28 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -63,6 +63,10 @@ extern int daemon(int, int); #include <sys/syscall.h> #endif +#ifdef __FreeBSD__ +#include <sys/sysctl.h> +#endif + int qemu_get_thread_id(void) { #if defined(__linux__) diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index 45113b464d..960d7f5d42 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -420,7 +420,7 @@ void qemu_thread_create(QemuThread *thread, const char *name, if (err) error_exit(err, __func__); -#ifdef _GNU_SOURCE +#if defined(__GLIBC__) && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 12)) if (name_threads) { pthread_setname_np(thread->thread, name); } diff --git a/util/rfifolock.c b/util/rfifolock.c new file mode 100644 index 0000000000..afbf7488df --- /dev/null +++ b/util/rfifolock.c @@ -0,0 +1,78 @@ +/* + * Recursive FIFO lock + * + * Copyright Red Hat, Inc. 2013 + * + * Authors: + * Stefan Hajnoczi <stefanha@redhat.com> + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + * + */ + +#include <assert.h> +#include "qemu/rfifolock.h" + +void rfifolock_init(RFifoLock *r, void (*cb)(void *), void *opaque) +{ + qemu_mutex_init(&r->lock); + r->head = 0; + r->tail = 0; + qemu_cond_init(&r->cond); + r->nesting = 0; + r->cb = cb; + r->cb_opaque = opaque; +} + +void rfifolock_destroy(RFifoLock *r) +{ + qemu_cond_destroy(&r->cond); + qemu_mutex_destroy(&r->lock); +} + +/* + * Theory of operation: + * + * In order to ensure FIFO ordering, implement a ticketlock. Threads acquiring + * the lock enqueue themselves by incrementing the tail index. When the lock + * is unlocked, the head is incremented and waiting threads are notified. + * + * Recursive locking does not take a ticket since the head is only incremented + * when the outermost recursive caller unlocks. + */ +void rfifolock_lock(RFifoLock *r) +{ + qemu_mutex_lock(&r->lock); + + /* Take a ticket */ + unsigned int ticket = r->tail++; + + if (r->nesting > 0 && qemu_thread_is_self(&r->owner_thread)) { + r->tail--; /* put ticket back, we're nesting */ + } else { + while (ticket != r->head) { + /* Invoke optional contention callback */ + if (r->cb) { + r->cb(r->cb_opaque); + } + qemu_cond_wait(&r->cond, &r->lock); + } + } + + qemu_thread_get_self(&r->owner_thread); + r->nesting++; + qemu_mutex_unlock(&r->lock); +} + +void rfifolock_unlock(RFifoLock *r) +{ + qemu_mutex_lock(&r->lock); + assert(r->nesting > 0); + assert(qemu_thread_is_self(&r->owner_thread)); + if (--r->nesting == 0) { + r->head++; + qemu_cond_broadcast(&r->cond); + } + qemu_mutex_unlock(&r->lock); +} |