Re: Instabilities with multi threaded application

On Fri, 2004-07-23 at 14:27 +0200, Philip Van Hoof wrote:

> Queue * new_Queue (gpointer host)
> {
> 	Queue *queue = (Queue*)g_malloc(sizeof (Queue));
> 	queue->app = host;
> 	queue->add_item = add_item;
> 	queue->cleanup = cleanup;
> 	queue->items = NULL;
> 	pthread_mutex_init (&queue->items_mutex, NULL);
> 	return queue;
> }

Why aren't you using a GAsyncQueue?

> static void * thread_main_func (void * data)
> {
> 	Queue *queue = (Queue*)data;
> 	while (queue->items)

This is unsafe.  Use: while ((item = g_async_queue_try_pop(queue)))

> 	if (g_list_length (queue->items) == 1)
> 	{
> 	 pthread_create (&queue->thread, NULL, thread_main_func, queue);
> 	}

This seems like a race condition that will create multiple consumer
threads in some cases (not to mention it being unsafe to call
g_list_length on a list being modified by another thread).  In that
case, you will certainly have a bigger problem as multiple consumer
threads try to process an item (item access isn't locked).

> While most of the times this works perfectly, I am getting 
> Xlib: unexpected async reply (sequence 0x46c)!
> When I click the GtkDrawingArea to fast. The thread which is created to
> process queued items will get killed by a segmentation error.

Use a GAsyncQueue, and only create the thread once, and have it simply
block on item retrieval.

Attachment: signature.asc
Description: This is a digitally signed message part

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]