如何使用 POSIX 线程声明递归互斥体？

发布于 2024-11-29 09:02:24 字数 547 浏览 1 评论 0原文

我对如何使用 pthread 声明递归互斥体有点困惑。我尝试做的是一次只有一个线程能够运行一段代码（包括函数），但在怀疑之后我发现使用互斥体不起作用，而我应该使用递归互斥体。这是我的代码：

pthread_mutex_lock(&mutex);                   // LOCK

item = queue_peek(queue);                     // get last item in queue
item_buff=item;                               // save item to a buffer
queue_removelast(queue);                      // remove last item from queue

pthread_mutex_unlock(&mutex);                 // UNLOCK

所以我尝试做的只是从队列中串行读取/删除。

问题是没有任何关于如何声明递归互斥体的示例。或者可能有一些，但它们不适合我编译。

原文

I am a bit confused on how to declare a recursive mutex using pthread.
What I try to do is have only one thread at a time be able to run a piece of code(including functions) but after scepticism I figured out that the use of mutexes would not work and that instead I should use recursive mutexes. Here is my code:

pthread_mutex_lock(&mutex);                   // LOCK

item = queue_peek(queue);                     // get last item in queue
item_buff=item;                               // save item to a buffer
queue_removelast(queue);                      // remove last item from queue

pthread_mutex_unlock(&mutex);                 // UNLOCK

So what I try to do is just read/remove from the queue serially.

The thing is that there isn't any example out there on how to declare recursive mutexes. Or there maybe a few but they don't compile for me.

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悍妇囚夫 2024-12-06 09:02:24

Michael Foukarakis 的代码几乎不错，但他初始化了互斥体两次，这导致了未定义的行为。它应该是：

pthread_mutex_t Mutex;
pthread_mutexattr_t Attr;

pthread_mutexattr_init(&Attr);
pthread_mutexattr_settype(&Attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&Mutex, &Attr);

我实际上在生产中使用了这段代码，并且我知道它可以在 Linux、Solaris、HP-UX、AIX、Mac OSX 和 FreeBSD 上正常工作。

您还需要添加适当的链接器标志来编译它：

AIX, Linux, FreeBSD:
CPLATFORM += -pthread

mingw32:
LDFLAGS += -lpthread

The code from Michael Foukarakis is almost good but he initializes the mutex twice which leads to undefined behavior. It should just be:

pthread_mutex_t Mutex;
pthread_mutexattr_t Attr;

pthread_mutexattr_init(&Attr);
pthread_mutexattr_settype(&Attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&Mutex, &Attr);

I actually use this code in production, and I know it works correctly on Linux, Solaris, HP-UX, AIX, Mac OSX and FreeBSD.

You also need to add proper linker flag to compile this:

AIX, Linux, FreeBSD:
CPLATFORM += -pthread

mingw32:
LDFLAGS += -lpthread

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小梨窩很甜 2024-12-06 09:02:24

要创建递归互斥体，您可以使用：

#include <pthread.h>
/* Don't forget to check the return value! */
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);

其中 type 为 PTHREAD_MUTEX_RECURSIVE 或初始化程序。

例如：

/* ..or PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP */
pthread_mutex_t       mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutexattr_t   mta;

或者，在运行时初始化（不要同时进行，这是未定义的行为）：

pthread_mutexattr_init(&mta);
/* or PTHREAD_MUTEX_RECURSIVE_NP */
pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_RECURSIVE);

pthread_mutex_init(&mutex, &mta);

To create a recursive mutex, you can either use:

#include <pthread.h>
/* Don't forget to check the return value! */
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);

where type is PTHREAD_MUTEX_RECURSIVE, or an initialiser.

For example:

/* ..or PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP */
pthread_mutex_t       mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutexattr_t   mta;

or alternatively, initialize at runtime (don't do both, it's undefined behaviour):

pthread_mutexattr_init(&mta);
/* or PTHREAD_MUTEX_RECURSIVE_NP */
pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_RECURSIVE);

pthread_mutex_init(&mutex, &mta);

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许你一世情深 2024-12-06 09:02:24

在 Linux 上（但这不能移植到其他系统），如果互斥体是全局变量或静态变量，您可以像这样初始化它

static pthread_mutex_t recmutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

（顺便说一句，示例来自 pthread_mutex_init(3) < em>手册页！）

On Linux (but this is non portable to other systems), if the mutex is a global or static variable, you could initialize it like

static pthread_mutex_t recmutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

(and by the way, the example is from pthread_mutex_init(3) man pages!)

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无所的.畏惧 2024-12-06 09:02:24

创建互斥体时需要添加互斥体属性。

调用 pthread_mutexattr_init，然后使用 PTHREAD_MUTEX_RECURSIVE 调用 pthread_mutexattr_settype，然后通过 pthread_mutex_init 使用这些属性。阅读 man pthread_mutexattr_init 来了解更多信息。