linux pthread_mutex_lock有惊群效应吗
时间: 2023-11-10 15:41:43 浏览: 44
是的,Linux pthread_mutex_lock 函数会产生惊群效应。惊群效应是指当一个进程等待某个资源时,其他进程也在等待这个资源,当这个资源可用时,多个进程同时被唤醒,导致系统性能下降。
在 pthread_mutex_lock 函数中,如果多个线程等待同一个互斥锁,当这个互斥锁可用时,所有等待它的线程都会被唤醒,这就会导致惊群效应。为了避免惊群效应,可以使用 pthread_cond_signal 或 pthread_cond_broadcast 函数来通知等待的线程,只有一个线程能够获得互斥锁。
另外,Linux 内核中针对惊群效应的问题,提供了 Futex(Fast User-Space Mutex)机制,它能够在用户态进行快速的互斥操作,并且能够避免惊群效应。
相关问题
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER; 是一个静态初始化互斥锁的方法。这个方法会将互斥锁的属性设置为默认值,并将互斥锁的状态设置为未锁定状态。这个方法可以用于在程序中定义一个互斥锁变量并初始化它,以便在后续的代码中使用。需要注意的是,这个方法只能用于静态初始化,如果需要在运行时动态初始化互斥锁,需要使用 pthread_mutex_init() 函数。
引用中提到了 pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;,这与 pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER; 是等价的,只是变量名不同而已。
引用中介绍了 pthread_mutex_lock()、pthread_mutex_unlock() 和 pthread_mutex_trylock() 这三个函数,它们都是用于操作互斥锁的。pthread_mutex_lock() 用于获取互斥锁,如果互斥锁已经被占用,则会阻塞等待;pthread_mutex_unlock() 用于释放互斥锁;pthread_mutex_trylock() 与 pthread_mutex_lock() 类似,但是如果互斥锁已经被占用,则会立即返回 EBUSY 错误码,而不是阻塞等待。
Linux man pthread_mutex_trylock
pthread_mutex_trylock is a function in Linux man pages that attempts to lock a mutex object. It is a non-blocking function that returns immediately, either locking the mutex and returning zero, or not locking the mutex and returning a non-zero value. The function prototype is as follows:
```c
#include <pthread.h>
int pthread_mutex_trylock(pthread_mutex_t *mutex);
```
Here, `mutex` is a pointer to the mutex object that you want to lock. If the mutex is already locked by another thread, `pthread_mutex_trylock` will return a non-zero value (typically `EBUSY`), and the mutex remains unchanged. If the mutex is successfully locked, the function will return zero.
It's important to note that `pthread_mutex_trylock` differs from `pthread_mutex_lock`, as the latter blocks the calling thread until the mutex becomes available, while `pthread_mutex_trylock` returns immediately regardless of the mutex's state.
Please let me know if you have any more questions!