Add support for LinuxThreads.

When using LinuxThreads pthread_setspecific triggers recursive
allocation on all threads. Work around this by creating a global linked
list of in-progress tsd initializations.

This modifies the _tsd_get_wrapper macro-generated function. When it has
to initialize an TSD object it will push the item to the linked list
first. If this causes a recursive allocation then the _get_wrapper
request is satisfied from the list. When pthread_setspecific returns the
item is removed from the list.

This effectively adds a very poor substitute for real TLS used only
during pthread_setspecific allocation recursion.

Signed-off-by: Crestez Dan Leonard <lcrestez@ixiacom.com>

src/tsd.c

@@ -105,3 +105,37 @@ JEMALLOC_SECTION(".CRT$XLY") JEMALLOC_ATTR(used)
 static const BOOL	(WINAPI *tls_callback)(HINSTANCE hinstDLL,
     DWORD fdwReason, LPVOID lpvReserved) = _tls_callback;
 #endif
+
+#if (!defined(JEMALLOC_MALLOC_THREAD_CLEANUP) && !defined(JEMALLOC_TLS) && \
+    !defined(_WIN32))
+void *
+tsd_init_check_recursion(tsd_init_head_t *head, tsd_init_block_t *block)
+{
+	pthread_t self = pthread_self();
+	tsd_init_block_t *iter;
+
+	/* Check whether this thread has already inserted into the list. */
+	malloc_mutex_lock(&head->lock);
+	ql_foreach(iter, &head->blocks, link) {
+		if (iter->thread == self) {
+			malloc_mutex_unlock(&head->lock);
+			return (iter->data);
+		}
+	}
+	/* Insert block into list. */
+	ql_elm_new(block, link);
+	block->thread = self;
+	ql_tail_insert(&head->blocks, block, link);
+	malloc_mutex_unlock(&head->lock);
+	return (NULL);
+}
+
+void
+tsd_init_finish(tsd_init_head_t *head, tsd_init_block_t *block)
+{
+
+	malloc_mutex_lock(&head->lock);
+	ql_remove(&head->blocks, block, link);
+	malloc_mutex_unlock(&head->lock);
+}
+#endif