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/*
* Recursive FIFO lock
*
* Copyright Red Hat, Inc. 2013
*
* Authors:
* Stefan Hajnoczi <stefanha@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#ifndef QEMU_RFIFOLOCK_H
#define QEMU_RFIFOLOCK_H
#include "qemu/thread.h"
/* Recursive FIFO lock
*
* This lock provides more features than a plain mutex:
*
* 1. Fairness - enforces FIFO order.
* 2. Nesting - can be taken recursively.
* 3. Contention callback - optional, called when thread must wait.
*
* The recursive FIFO lock is heavyweight so prefer other synchronization
* primitives if you do not need its features.
*/
typedef struct {
QemuMutex lock; /* protects all fields */
/* FIFO order */
unsigned int head; /* active ticket number */
unsigned int tail; /* waiting ticket number */
QemuCond cond; /* used to wait for our ticket number */
/* Nesting */
QemuThread owner_thread; /* thread that currently has ownership */
unsigned int nesting; /* amount of nesting levels */
/* Contention callback */
void (*cb)(void *); /* called when thread must wait, with ->lock
* held so it may not recursively lock/unlock
*/
void *cb_opaque;
} RFifoLock;
void rfifolock_init(RFifoLock *r, void (*cb)(void *), void *opaque);
void rfifolock_destroy(RFifoLock *r);
void rfifolock_lock(RFifoLock *r);
void rfifolock_unlock(RFifoLock *r);
#endif /* QEMU_RFIFOLOCK_H */
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