GThreadPool

typedef struct {
  GFunc func;
  gpointer user_data;
  gboolean exclusive;
} GThreadPool;

The GThreadPool struct represents a thread pool. It has six public read-only members, but the underlying struct is bigger, so you must not copy this struct.

g_thread_pool_new ()

GThreadPool* g_thread_pool_new              (GFunc func,
                                             gpointer user_data,
                                             gint max_threads,
                                             gboolean exclusive,
                                             GError **error);

This function creates a new thread pool.

Whenever you call g_thread_pool_push(), either a new thread is created or an unused one is reused. At most max_threads threads are running concurrently for this thread pool. max_threads = -1 allows unlimited threads to be created for this thread pool. The newly created or reused thread now executes the function func with the two arguments. The first one is the parameter to g_thread_pool_push() and the second one is user_data.

The parameter exclusive determines, whether the thread pool owns all threads exclusive or whether the threads are shared globally. If exclusive is TRUE, max_threads threads are started immediately and they will run exclusively for this thread pool until it is destroyed by g_thread_pool_free(). If exclusive is FALSE, threads are created, when needed and shared between all non-exclusive thread pools. This implies that max_threads may not be -1 for exclusive thread pools.

error can be NULL to ignore errors, or non-NULL to report errors. An error can only occur when exclusive is set to TRUE and not all max_threads threads could be created.

g_thread_pool_push ()

void        g_thread_pool_push              (GThreadPool *pool,
                                             gpointer data,
                                             GError **error);

Inserts data into the list of tasks to be executed by pool. When the number of currently running threads is lower than the maximal allowed number of threads, a new thread is started (or reused) with the properties given to g_thread_pool_new(). Otherwise data stays in the queue until a thread in this pool finishes its previous task and processes data.

error can be NULL to ignore errors, or non-NULL to report errors. An error can only occur when a new thread couldn't be created. In that case data is simply appended to the queue of work to do.

g_thread_pool_set_max_threads ()

void        g_thread_pool_set_max_threads   (GThreadPool *pool,
                                             gint max_threads,
                                             GError **error);

Sets the maximal allowed number of threads for pool. A value of -1 means, that the maximal number of threads is unlimited.

Setting max_threads to 0 means stopping all work for pool. It is effectively frozen until max_threads is set to a non-zero value again.

A thread is never terminated while calling func, as supplied by g_thread_pool_new(). Instead the maximal number of threads only has effect for the allocation of new threads in g_thread_pool_push(). A new thread is allocated, whenever the number of currently running threads in pool is smaller than the maximal number.

error can be NULL to ignore errors, or non-NULL to report errors. An error can only occur when a new thread couldn't be created.

g_thread_pool_get_max_threads ()

gint        g_thread_pool_get_max_threads   (GThreadPool *pool);

Returns the maximal number of threads for pool.

g_thread_pool_get_num_threads ()

guint       g_thread_pool_get_num_threads   (GThreadPool *pool);

Returns the number of threads currently running in pool.

g_thread_pool_unprocessed ()

guint       g_thread_pool_unprocessed       (GThreadPool *pool);

Returns the number of tasks still unprocessed in pool.

g_thread_pool_free ()

void        g_thread_pool_free              (GThreadPool *pool,
                                             gboolean immediate,
                                             gboolean wait);

Frees all resources allocated for pool.

If immediate is TRUE, no new task is processed for pool. Otherwise pool is not freed before the last task is processed. Note however, that no thread of this pool is interrupted, while processing a task. Instead at least all still running threads can finish their tasks before the pool is freed.

If wait is TRUE, the functions does not return before all tasks to be processed (dependent on immediate, whether all or only the currently running) are ready. Otherwise the function returns immediately.

After calling this function pool must not be used anymore.

g_thread_pool_set_max_unused_threads ()

void        g_thread_pool_set_max_unused_threads
                                            (gint max_threads);

Sets the maximal number of unused threads to max_threads. If max_threads is -1, no limit is imposed on the number of unused threads.

g_thread_pool_get_max_unused_threads ()

gint        g_thread_pool_get_max_unused_threads
                                            (void);

Returns the maximal allowed number of unused threads.

g_thread_pool_get_num_unused_threads ()

guint       g_thread_pool_get_num_unused_threads
                                            (void);

Returns the number of currently unused threads.

g_thread_pool_stop_unused_threads ()

void        g_thread_pool_stop_unused_threads
                                            (void);

Stops all currently unused threads. This does not change the maximal number of unused threads. This function can be used to regularly stop all unused threads e.g. from g_timeout_add().