branches/zip: Add instrumentation for prohibiting the release of

the buffer pool mutex.  The instrumentation can be activated by
defining UNIV_DEBUG or UNIV_BUF_DEBUG at compilation time.

buf_pool_mutex_exit_forbidden: New variable.  When this is nonzero,
an assertion will fail in buf_pool_mutex_exit().

buf_pool_mutex_exit_forbid(): Macro for declaring that the buffer pool
mutex must not be released.  Calls may be nested.

buf_pool_mutex_exit_allow(): Macro for declaring that the buffer pool
mutex may be released.  Calls may be nested.

buf_LRU_search_and_free_block(): Prohibit buf_pool_mutex_exit() in the
scope of the function.

buf_LRU_free_block(): Prohibit buf_pool_mutex_exit() in buf_buddy_alloc()
and buf_buddy_free().

buf_LRU_block_remove_hashed_page(): Prohibit buf_pool_mutex_exit()
in buf_buddy_free().

buf/buf0buf.c

@@ -235,6 +235,9 @@ mutex_t		buf_pool_zip_mutex;
 static ulint	buf_dbg_counter	= 0; /* This is used to insert validation
 					operations in excution in the
 					debug version */
+/** Flag to forbid the release of the buffer pool mutex.
+Protected by buf_pool->mutex. */
+ulint		buf_pool_mutex_exit_forbidden = 0;
 #endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
 #ifdef UNIV_DEBUG
 ibool		buf_debug_prints = FALSE; /* If this is set TRUE,

buf/buf0lru.c

@@ -267,6 +267,7 @@ buf_LRU_search_and_free_block(
 	ibool		freed;
 
 	buf_pool_mutex_enter();
+	buf_pool_mutex_exit_forbid();
 
 	freed = FALSE;
 	bpage = UT_LIST_GET_LAST(buf_pool->LRU);
@@ -355,6 +356,7 @@ buf_LRU_search_and_free_block(
 	if (!freed) {
 		buf_pool->LRU_flush_ended = 0;
 	}
+	buf_pool_mutex_exit_allow();
 	buf_pool_mutex_exit();
 
 	return(freed);
@@ -983,7 +985,9 @@ buf_LRU_free_block(
 		If it cannot be allocated (without freeing a block
 		from the LRU list), refuse to free bpage. */
 alloc:
+		buf_pool_mutex_exit_forbid();
 		b = buf_buddy_alloc(sizeof *b, NULL);
+		buf_pool_mutex_exit_allow();
 
 		if (UNIV_UNLIKELY(!b)) {
 			return(FALSE);
@@ -1155,7 +1159,9 @@ buf_LRU_block_free_non_file_page(
 	if (data) {
 		block->page.zip.data = NULL;
 		mutex_exit(&block->mutex);
+		buf_pool_mutex_exit_forbid();
 		buf_buddy_free(data, page_zip_get_size(&block->page.zip));
+		buf_pool_mutex_exit_allow();
 		mutex_enter(&block->mutex);
 		page_zip_set_size(&block->page.zip, 0);
 	}
@@ -1305,9 +1311,11 @@ buf_LRU_block_remove_hashed_page(
 		UT_LIST_REMOVE(list, buf_pool->zip_clean, bpage);
 
 		mutex_exit(&buf_pool_zip_mutex);
+		buf_pool_mutex_exit_forbid();
 		buf_buddy_free(bpage->zip.data,
 			       page_zip_get_size(&bpage->zip));
 		buf_buddy_free(bpage, sizeof(*bpage));
+		buf_pool_mutex_exit_allow();
 		UNIV_MEM_UNDESC(bpage);
 		return(BUF_BLOCK_ZIP_FREE);
 

include/buf0buf.h

@@ -1277,8 +1277,35 @@ buf_pool_mutex directly. */
 	ut_ad(!mutex_own(&buf_pool_zip_mutex));	\
 	mutex_enter(&buf_pool_mutex);		\
 } while (0)
+
+#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
+/** Flag to forbid the release of the buffer pool mutex.
+Protected by buf_pool_mutex. */
+extern ulint	buf_pool_mutex_exit_forbidden;
+/* Forbid the release of the buffer pool mutex. */
+# define buf_pool_mutex_exit_forbid() do {	\
+	ut_ad(buf_pool_mutex_own());		\
+	buf_pool_mutex_exit_forbidden++;	\
+} while (0)
+/* Allow the release of the buffer pool mutex. */
+# define buf_pool_mutex_exit_allow() do {	\
+	ut_ad(buf_pool_mutex_own());		\
+	ut_a(buf_pool_mutex_exit_forbidden);	\
+	buf_pool_mutex_exit_forbidden--;	\
+} while (0)
 /* Release the buffer pool mutex. */
-#define buf_pool_mutex_exit() mutex_exit(&buf_pool_mutex)
+# define buf_pool_mutex_exit() do {		\
+	ut_a(!buf_pool_mutex_exit_forbidden);	\
+	mutex_exit(&buf_pool_mutex);		\
+} while (0)
+#else
+/* Forbid the release of the buffer pool mutex. */
+# define buf_pool_mutex_exit_forbid() ((void) 0)
+/* Allow the release of the buffer pool mutex. */
+# define buf_pool_mutex_exit_allow() ((void) 0)
+/* Release the buffer pool mutex. */
+# define buf_pool_mutex_exit() mutex_exit(&buf_pool_mutex)
+#endif
 
 /************************************************************************
 Let us list the consistency conditions for different control block states.