Fix bugs in datum_queue_free

[jesterhodl]

1. q->buffer[1] doesn't seem to be free()'d

2. q->buffer[0] is duplicated, you probably meant to zero out buffer[1]

3. shouldn't the unlocking order be reverse of locking order to prevent deadlocks?

[wizkid057]

buffer[1] cannot be free'd because its allocated in a single call for buffer[0] and then split.

datum_gateway/src/datum_queue.c

Line 117 in a384ff6

q->buffer[1] = ((char *)q->buffer[0]) + ((max_items + 16) * item_size);

[wizkid057]

Looking at the locks, in this case the goal is to acquire all locks as write locks, which, once acquired, prevents other threads from acquiring the locks at all until released. There's no contention possible on the ordering of unlocking since the cleanup function has the sole lock at that point.

The unsetting of [0] twice is a bug, though.

Looking more closely, there may be a race issue where the "datum_queue_free" function frees data while a "datum_queue_add_item" tries to get a lock that's already destroyed. Probably need to check if the buffer ptr is not null around here before trying to get the lock.

[jesterhodl]

I'm reading through the code, but I think I found one more thing.
Don't we have a one 0 too much in the condition?

        for (i=0;i<10000000;i++) {
                if (i < 99999990)  // should be 9999999, anything larger doesn't make sense 
// 10000000
// 99999990

[wizkid057]

I'm reading through the code, but I think I found one more thing. Don't we have a one 0 too much in the condition?

        for (i=0;i<10000000;i++) {
                if (i < 99999990)  // should be 9999999, anything larger doesn't make sense 
// 10000000
// 99999990

Yep, seems so.

[jesterhodl]

Is this what you had in mind?

			pthread_rwlock_unlock(&q->active_buffer_rwlock);
			
			// Check potential race condition with datum_queue_free() before acquiring a lock
			if (q->buffer[buffer_id] == NULL) {
				DLOG_ERROR("Buffer pointer null. Queue already destroyed?");
				return -1;
			}
			
			// get a write lock for that buffer
			pthread_rwlock_wrlock(&q->buffer_rwlock[buffer_id]);

[luke-jr]

This was merged...