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/*
* Polymorphic locking functions (aka poor man templates)
*
* Copyright Red Hat, Inc. 2017, 2018
*
* Author: Paolo Bonzini <pbonzini@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.
*
*/
#ifndef QEMU_LOCKABLE_H
#define QEMU_LOCKABLE_H
#include "qemu/coroutine-core.h"
#include "qemu/thread.h"
typedef void QemuLockUnlockFunc(void *);
typedef struct QemuLockable {
void *object;
QemuLockUnlockFunc *lock;
QemuLockUnlockFunc *unlock;
} QemuLockable;
static inline __attribute__((__always_inline__)) QemuLockable *
qemu_make_lockable(void *x, QemuLockable *lockable)
{
/*
* We cannot test this in a macro, otherwise we get compiler
* warnings like "the address of 'm' will always evaluate as 'true'".
*/
return x ? lockable : NULL;
}
static inline __attribute__((__always_inline__)) QemuLockable *
qemu_null_lockable(void *x)
{
if (x != NULL) {
qemu_build_not_reached();
}
return NULL;
}
/*
* In C, compound literals have the lifetime of an automatic variable.
* In C++ it would be different, but then C++ wouldn't need QemuLockable
* either...
*/
#define QML_OBJ_(x, name) (&(QemuLockable) { \
.object = (x), \
.lock = (QemuLockUnlockFunc *) qemu_ ## name ## _lock, \
.unlock = (QemuLockUnlockFunc *) qemu_ ## name ## _unlock \
})
/**
* QEMU_MAKE_LOCKABLE - Make a polymorphic QemuLockable
*
* @x: a lock object (currently one of QemuMutex, QemuRecMutex,
* CoMutex, QemuSpin).
*
* Returns a QemuLockable object that can be passed around
* to a function that can operate with locks of any kind, or
* NULL if @x is %NULL.
*
* Note the special case for void *, so that we may pass "NULL".
*/
#define QEMU_MAKE_LOCKABLE(x) \
_Generic((x), QemuLockable *: (x), \
void *: qemu_null_lockable(x), \
QemuMutex *: qemu_make_lockable(x, QML_OBJ_(x, mutex)), \
QemuRecMutex *: qemu_make_lockable(x, QML_OBJ_(x, rec_mutex)), \
CoMutex *: qemu_make_lockable(x, QML_OBJ_(x, co_mutex)), \
QemuSpin *: qemu_make_lockable(x, QML_OBJ_(x, spin)))
/**
* QEMU_MAKE_LOCKABLE_NONNULL - Make a polymorphic QemuLockable
*
* @x: a lock object (currently one of QemuMutex, QemuRecMutex,
* CoMutex, QemuSpin).
*
* Returns a QemuLockable object that can be passed around
* to a function that can operate with locks of any kind.
*/
#define QEMU_MAKE_LOCKABLE_NONNULL(x) \
_Generic((x), QemuLockable *: (x), \
QemuMutex *: QML_OBJ_(x, mutex), \
QemuRecMutex *: QML_OBJ_(x, rec_mutex), \
CoMutex *: QML_OBJ_(x, co_mutex), \
QemuSpin *: QML_OBJ_(x, spin))
static inline void qemu_lockable_lock(QemuLockable *x)
{
x->lock(x->object);
}
static inline void qemu_lockable_unlock(QemuLockable *x)
{
x->unlock(x->object);
}
static inline QemuLockable *qemu_lockable_auto_lock(QemuLockable *x)
{
qemu_lockable_lock(x);
return x;
}
static inline void qemu_lockable_auto_unlock(QemuLockable *x)
{
if (x) {
qemu_lockable_unlock(x);
}
}
G_DEFINE_AUTOPTR_CLEANUP_FUNC(QemuLockable, qemu_lockable_auto_unlock)
#define WITH_QEMU_LOCK_GUARD_(x, var) \
for (g_autoptr(QemuLockable) var = \
qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))); \
var; \
qemu_lockable_auto_unlock(var), var = NULL)
/**
* WITH_QEMU_LOCK_GUARD - Lock a lock object for scope
*
* @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
*
* This macro defines a lock scope such that entering the scope takes the lock
* and leaving the scope releases the lock. Return statements are allowed
* within the scope and release the lock. Break and continue statements leave
* the scope early and release the lock.
*
* WITH_QEMU_LOCK_GUARD(&mutex) {
* ...
* if (error) {
* return; <-- mutex is automatically unlocked
* }
*
* if (early_exit) {
* break; <-- leave this scope early
* }
* ...
* }
*/
#define WITH_QEMU_LOCK_GUARD(x) \
WITH_QEMU_LOCK_GUARD_((x), glue(qemu_lockable_auto, __COUNTER__))
/**
* QEMU_LOCK_GUARD - Lock an object until the end of the scope
*
* @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
*
* This macro takes a lock until the end of the scope. Return statements
* release the lock.
*
* ... <-- mutex not locked
* QEMU_LOCK_GUARD(&mutex); <-- mutex locked from here onwards
* ...
* if (error) {
* return; <-- mutex is automatically unlocked
* }
*/
#define QEMU_LOCK_GUARD(x) \
g_autoptr(QemuLockable) \
glue(qemu_lockable_auto, __COUNTER__) G_GNUC_UNUSED = \
qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE((x)))
#endif
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