2da61b671e
QemuMutex does not guarantee fairness and cannot be acquired recursively: Fairness means each locker gets a turn and the scheduler cannot cause starvation. Recursive locking is useful for composition, it allows a sequence of locking operations to be invoked atomically by acquiring the lock around them. This patch adds RFifoLock, a recursive lock that guarantees FIFO order. Its first user is added in the next patch. RFifoLock has one additional feature: it can be initialized with an optional contention callback. The callback is invoked whenever a thread must wait for the lock. For example, it can be used to poke the current owner so that they release the lock soon. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
92 lines
2.1 KiB
C
92 lines
2.1 KiB
C
/*
|
|
* RFifoLock tests
|
|
*
|
|
* 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 <glib.h>
|
|
#include "qemu-common.h"
|
|
#include "qemu/rfifolock.h"
|
|
|
|
static void test_nesting(void)
|
|
{
|
|
RFifoLock lock;
|
|
|
|
/* Trivial test, ensure the lock is recursive */
|
|
rfifolock_init(&lock, NULL, NULL);
|
|
rfifolock_lock(&lock);
|
|
rfifolock_lock(&lock);
|
|
rfifolock_lock(&lock);
|
|
rfifolock_unlock(&lock);
|
|
rfifolock_unlock(&lock);
|
|
rfifolock_unlock(&lock);
|
|
rfifolock_destroy(&lock);
|
|
}
|
|
|
|
typedef struct {
|
|
RFifoLock lock;
|
|
int fd[2];
|
|
} CallbackTestData;
|
|
|
|
static void rfifolock_cb(void *opaque)
|
|
{
|
|
CallbackTestData *data = opaque;
|
|
int ret;
|
|
char c = 0;
|
|
|
|
ret = write(data->fd[1], &c, sizeof(c));
|
|
g_assert(ret == 1);
|
|
}
|
|
|
|
static void *callback_thread(void *opaque)
|
|
{
|
|
CallbackTestData *data = opaque;
|
|
|
|
/* The other thread holds the lock so the contention callback will be
|
|
* invoked...
|
|
*/
|
|
rfifolock_lock(&data->lock);
|
|
rfifolock_unlock(&data->lock);
|
|
return NULL;
|
|
}
|
|
|
|
static void test_callback(void)
|
|
{
|
|
CallbackTestData data;
|
|
QemuThread thread;
|
|
int ret;
|
|
char c;
|
|
|
|
rfifolock_init(&data.lock, rfifolock_cb, &data);
|
|
ret = qemu_pipe(data.fd);
|
|
g_assert(ret == 0);
|
|
|
|
/* Hold lock but allow the callback to kick us by writing to the pipe */
|
|
rfifolock_lock(&data.lock);
|
|
qemu_thread_create(&thread, "callback_thread",
|
|
callback_thread, &data, QEMU_THREAD_JOINABLE);
|
|
ret = read(data.fd[0], &c, sizeof(c));
|
|
g_assert(ret == 1);
|
|
rfifolock_unlock(&data.lock);
|
|
/* If we got here then the callback was invoked, as expected */
|
|
|
|
qemu_thread_join(&thread);
|
|
close(data.fd[0]);
|
|
close(data.fd[1]);
|
|
rfifolock_destroy(&data.lock);
|
|
}
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
g_test_init(&argc, &argv, NULL);
|
|
g_test_add_func("/nesting", test_nesting);
|
|
g_test_add_func("/callback", test_callback);
|
|
return g_test_run();
|
|
}
|