libvirt/src/util/virthread.h

/*
 * virthread.h: basic thread synchronization primitives
 *
 * Copyright (C) 2009-2011, 2013-2014 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 */

#pragma once

#include "internal.h"
#include "virerror.h"

#include <pthread.h>

typedef struct virMutex virMutex;
struct virMutex {
    pthread_mutex_t lock;
};

typedef struct virLockGuard virLockGuard;
struct virLockGuard {
    virMutex *mutex;
};

typedef struct virRWLock virRWLock;
struct virRWLock {
    pthread_rwlock_t lock;
};


typedef struct virCond virCond;
struct virCond {
    pthread_cond_t cond;
};

typedef struct virThreadLocal virThreadLocal;
struct virThreadLocal {
    pthread_key_t key;
};

typedef struct virThread virThread;
struct virThread {
    pthread_t thread;
};

typedef struct virOnceControl virOnceControl;
struct virOnceControl {
    pthread_once_t once;
};


#define VIR_MUTEX_INITIALIZER \
    { \
        .lock = PTHREAD_MUTEX_INITIALIZER \
    }

#define VIR_ONCE_CONTROL_INITIALIZER \
    { \
        .once = PTHREAD_ONCE_INIT \
    }

typedef void (*virOnceFunc)(void);

typedef void (*virThreadFunc)(void *opaque);

#define virThreadCreate(thread, joinable, func, opaque) \
    virThreadCreateFull(thread, joinable, func, #func, false, opaque)

int virThreadCreateFull(virThread *thread,
                        bool joinable,
                        virThreadFunc func,
                        const char *name,
                        bool worker,
                        void *opaque) G_GNUC_WARN_UNUSED_RESULT;
void virThreadSelf(virThread *thread);
bool virThreadIsSelf(virThread *thread);
void virThreadJoin(virThread *thread);

size_t virThreadMaxName(void);

/* This API is *NOT* for general use. It exists solely as a stub
 * for integration with libselinux AVC callbacks */
void virThreadCancel(virThread *thread);

/* These next two functions are for debugging only, since they are not
 * guaranteed to give unique values for distinct threads on all
 * architectures, nor are the two functions guaranteed to give the same
 * value for the same thread. */
unsigned long long virThreadSelfID(void);
unsigned long long virThreadID(virThread *thread);

/* Static initialization of mutexes is not possible, so we instead
 * provide for guaranteed one-time initialization via a callback
 * function.  Usage:
 * static virOnceControl once = VIR_ONCE_CONTROL_INITIALIZER;
 * static void initializer(void) { ... }
 * void myfunc()
 * {
 *     if (virOnce(&once, initializer) < 0)
 *         goto error;
 *     ...now guaranteed that initializer has completed exactly once
 * }
 */
int virOnce(virOnceControl *once, virOnceFunc init)
    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) G_GNUC_WARN_UNUSED_RESULT;

int virMutexInit(virMutex *m) G_GNUC_WARN_UNUSED_RESULT;
int virMutexInitRecursive(virMutex *m) G_GNUC_WARN_UNUSED_RESULT;
void virMutexDestroy(virMutex *m);

void virMutexLock(virMutex *m);
void virMutexUnlock(virMutex *m);


virLockGuard virLockGuardLock(virMutex *m);
void virLockGuardUnlock(virLockGuard *l);
G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(virLockGuard, virLockGuardUnlock);
#define VIR_LOCK_GUARD g_auto(virLockGuard) G_GNUC_UNUSED

int virRWLockInit(virRWLock *m) G_GNUC_WARN_UNUSED_RESULT;
void virRWLockDestroy(virRWLock *m);

void virRWLockRead(virRWLock *m);
void virRWLockWrite(virRWLock *m);
void virRWLockUnlock(virRWLock *m);


int virCondInit(virCond *c) G_GNUC_WARN_UNUSED_RESULT;
int virCondDestroy(virCond *c);

/* virCondWait, virCondWaitUntil:
 * These functions can return without the associated predicate
 * changing value. Therefore in nearly all cases they
 * should be enclosed in a while loop that checks the predicate.
 */
int virCondWait(virCond *c, virMutex *m) G_GNUC_WARN_UNUSED_RESULT;
int virCondWaitUntil(virCond *c, virMutex *m, unsigned long long whenms) G_GNUC_WARN_UNUSED_RESULT;

void virCondSignal(virCond *c);
void virCondBroadcast(virCond *c);


typedef void (*virThreadLocalCleanup)(void *);
int virThreadLocalInit(virThreadLocal *l,
                       virThreadLocalCleanup c) G_GNUC_WARN_UNUSED_RESULT;
void *virThreadLocalGet(virThreadLocal *l);
int virThreadLocalSet(virThreadLocal *l, void*) G_GNUC_WARN_UNUSED_RESULT;


/**
 * VIR_ONCE_GLOBAL_INIT:
 * classname: base classname
 *
 * This macro simplifies the setup of a one-time only
 * global file initializer.
 *
 * Assuming a class called "virMyObject", and a method
 * implemented like:
 *
 *  int virMyObjectOnceInit(void) {
 *      ...do init tasks...
 *  }
 *
 * Then invoking the macro:
 *
 *  VIR_ONCE_GLOBAL_INIT(virMyObject);
 *
 * Will create a method
 *
 *  int virMyObjectInitialize(void);
 *
 * Which will ensure that 'virMyObjectOnceInit' is
 * guaranteed to be invoked exactly once.
 */
#define VIR_ONCE_GLOBAL_INIT(classname) \
    static virOnceControl classname ## OnceControl = VIR_ONCE_CONTROL_INITIALIZER; \
    static virErrorPtr classname ## OnceError; \
 \
    static void classname ## Once(void) \
    { \
        if (classname ## OnceInit() < 0) \
            classname ## OnceError = virSaveLastError(); \
    } \
 \
    static int classname ## Initialize(void) \
    { \
        if (virOnce(&classname ## OnceControl, classname ## Once) < 0) \
            return -1; \
 \
        if (classname ## OnceError) { \
            virSetError(classname ## OnceError); \
            return -1; \
        } \
 \
        return 0; \
    } \
    struct classname ## EatSemicolon

#define VIR_WITH_MUTEX_LOCK_GUARD_(m, name) \
    for (g_auto(virLockGuard) name = virLockGuardLock(m); name.mutex; \
        name.mutex = (virLockGuardUnlock(&name), NULL))
/**
 * VIR_WITH_MUTEX_LOCK_GUARD:
 *
 * 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.
 *
 *     virMutex *mutex = ...;
 *
 *     VIR_WITH_MUTEX_LOCK_GUARD(mutex) {
 *         // `mutex` is locked, and released automatically on scope exit
 *         ...
 *     }
 */
#define VIR_WITH_MUTEX_LOCK_GUARD(m) \
    VIR_WITH_MUTEX_LOCK_GUARD_(m, CONCAT(var, __COUNTER__))