Description [src]

union GMutex {
  /* No available fields */

The GMutex struct is an opaque data structure to represent a mutex (mutual exclusion). It can be used to protect data against shared access.

Take for example the following function:

  give_me_next_number (void)
    static int current_number = 0;

    // now do a very complicated calculation to calculate the new
    // number, this might for example be a random number generator
    current_number = calc_next_number (current_number);

    return current_number;

It is easy to see that this won’t work in a multi-threaded application. There current_number must be protected against shared access. A GMutex can be used as a solution to this problem:

  give_me_next_number (void)
    static GMutex mutex;
    static int current_number = 0;
    int ret_val;

    g_mutex_lock (&mutex);
    ret_val = current_number = calc_next_number (current_number);
    g_mutex_unlock (&mutex);

    return ret_val;

Notice that the GMutex is not initialised to any particular value. Its placement in static storage ensures that it will be initialised to all-zeros, which is appropriate.

If a GMutex is placed in other contexts (eg: embedded in a struct) then it must be explicitly initialised using g_mutex_init().

A GMutex should only be accessed via g_mutex_ functions.

Instance methods


Frees the resources allocated to a mutex with g_mutex_init().


Initializes a GMutex so that it can be used.

Available since: 2.32


Locks mutex. If mutex is already locked by another thread, the current thread will block until mutex is unlocked by the other thread.


Tries to lock mutex. If mutex is already locked by another thread, it immediately returns FALSE. Otherwise it locks mutex and returns TRUE.


Unlocks mutex. If another thread is blocked in a g_mutex_lock() call for mutex, it will become unblocked and can lock mutex itself.