Get a mutex type
#include <pthread.h> int pthread_mutexattr_gettype( const pthread_mutexattr_t * attr, int * type );
- A pointer to the pthread_mutexattr_t object that you want to get the attribute from.
- A pointer to a location where the function can store the type.
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The pthread_mutexattr_gettype() function gets the mutex type from the mutex attribute object attr and stores it in type. Valid mutex types include:
- No deadlock detection. A thread that attempts to relock this mutex without first unlocking it deadlocks. Attempts to unlock a mutex locked by a different thread or attempts to unlock an unlocked mutex result in undefined behavior.
- Provides error checking.
A thread returns with an error when it attempts to:
- Relock this mutex without first unlocking it.
- Unlock a mutex that another thread has locked.
- Unlock an unlocked mutex.
- A thread that attempts to relock this mutex without first unlocking it succeeds in locking the mutex. The relocking deadlock that can occur with mutexes of type PTHREAD_MUTEX_NORMAL can't occur with this mutex type. Multiple locks of this mutex require the same number of unlocks to release the mutex before another thread can acquire the mutex. A thread that attempts to unlock a mutex that another thread has locked, or unlock an unlocked mutex, returns with an error.
- The default value of the type attribute. Attempts to recursively lock a mutex of this type, or unlock a mutex of this type that isn't locked by the calling thread, or unlock a mutex of this type that isn't locked, results in undefined behavior.
- Invalid mutex attribute object attr.
An application shouldn't use a PTHREAD_MUTEX_RECURSIVE mutex with condition variables because the implicit unlock performed for a pthread_cond_wait() or pthread_cond_timedwait() may not actually release the mutex (if it's been locked multiple times). If this happens, no other thread can satisfy the condition of the predicate.