This ChangeSet must be null-merged to 5.1. Applied innodb-5.0-ss982, -ss998, -ss1003

Fixes:
- Bug #15815: Very poor performance with multiple queries running concurrently
- Bug #22868: 'Thread thrashing' with > 50 concurrent conns under an upd-intensive workloadw
- Bug #23769: Debug assertion failure with innodb_locks_unsafe_for_binlog
- Bug #24089: Race condition in fil_flush_file_spaces()

3 files changed, 214 insertions, 84 deletions

diff --git a/innobase/buf/buf0buf.c b/innobase/buf/buf0buf.c
index db09a931c29..f24f1744363 100644
--- a/innobase/buf/buf0buf.c
+++ b/innobase/buf/buf0buf.c
@@ -221,6 +221,9 @@ in the free list to the frames.
 5) When we have AWE enabled, we disable adaptive hash indexes.
 */
 
+/* Value in microseconds */
+static const int WAIT_FOR_READ	= 20000;
+
 buf_pool_t*	buf_pool = NULL; /* The buffer buf_pool of the database */
 
 #ifdef UNIV_DEBUG
@@ -488,6 +491,9 @@ buf_block_init(
 
 	block->n_pointers = 0;
 
+	mutex_create(&block->mutex);
+	mutex_set_level(&block->mutex, SYNC_BUF_BLOCK);
+
 	rw_lock_create(&(block->lock));
 	ut_ad(rw_lock_validate(&(block->lock)));
 
@@ -756,8 +762,15 @@ buf_awe_map_page_to_frame(
 	bck = UT_LIST_GET_LAST(buf_pool->awe_LRU_free_mapped);
 
 	while (bck) {	
-		if (bck->state == BUF_BLOCK_FILE_PAGE
-	    	    && (bck->buf_fix_count != 0 || bck->io_fix != 0)) {
+		ibool skip;
+
+		mutex_enter(&bck->mutex);
+
+		skip = (bck->state == BUF_BLOCK_FILE_PAGE
+			&& (bck->buf_fix_count != 0 || bck->io_fix != 0));
+
+		if (skip) {
+			mutex_exit(&bck->mutex);
 
 			/* We have to skip this */
 			bck = UT_LIST_GET_PREV(awe_LRU_free_mapped, bck);
@@ -790,6 +803,8 @@ buf_awe_map_page_to_frame(
 
 			buf_pool->n_pages_awe_remapped++;
 			
+			mutex_exit(&bck->mutex);
+
 			return;
 		}
 	}
@@ -828,13 +843,22 @@ buf_block_make_young(
 /*=================*/
 	buf_block_t*	block)	/* in: block to make younger */
 {
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(!mutex_own(&(buf_pool->mutex)));
+#endif /* UNIV_SYNC_DEBUG */
+
+	/* Note that we read freed_page_clock's without holding any mutex:
+	this is allowed since the result is used only in heuristics */
+
 	if (buf_pool->freed_page_clock >= block->freed_page_clock 
-				+ 1 + (buf_pool->curr_size / 1024)) {
+				+ 1 + (buf_pool->curr_size / 4)) {
 
+		mutex_enter(&buf_pool->mutex);
 		/* There has been freeing activity in the LRU list:
 		best to move to the head of the LRU list */
 
 		buf_LRU_make_block_young(block);
+		mutex_exit(&buf_pool->mutex);
 	}
 }
 
@@ -869,12 +893,16 @@ buf_block_free(
 /*===========*/
 	buf_block_t*	block)	/* in, own: block to be freed */
 {
-	ut_a(block->state != BUF_BLOCK_FILE_PAGE);
-
 	mutex_enter(&(buf_pool->mutex));
 
+	mutex_enter(&block->mutex);
+
+	ut_a(block->state != BUF_BLOCK_FILE_PAGE);
+
 	buf_LRU_block_free_non_file_page(block);
 
+	mutex_exit(&block->mutex);
+
 	mutex_exit(&(buf_pool->mutex));
 }
 
@@ -1093,9 +1121,8 @@ buf_page_get_gen(
 #endif
 	buf_pool->n_page_gets++;
 loop:
-	mutex_enter_fast(&(buf_pool->mutex));
-
 	block = NULL;
+	mutex_enter_fast(&(buf_pool->mutex));
 	
 	if (guess) {
 		block = buf_block_align(guess);
@@ -1133,6 +1160,8 @@ loop:
 		goto loop;
 	}
 
+	mutex_enter(&block->mutex);
+
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
 	must_read = FALSE;
@@ -1142,9 +1171,9 @@ loop:
 		must_read = TRUE;
 
 		if (mode == BUF_GET_IF_IN_POOL) {
-
 			/* The page is only being read to buffer */
-			mutex_exit(&(buf_pool->mutex));
+			mutex_exit(&buf_pool->mutex);
+			mutex_exit(&block->mutex);
 
 			return(NULL);
 		}
@@ -1168,7 +1197,7 @@ loop:
 #else
 	buf_block_buf_fix_inc(block);
 #endif
-	buf_block_make_young(block);
+	mutex_exit(&buf_pool->mutex);
 
 	/* Check if this is the first access to the page */
 
@@ -1176,10 +1205,13 @@ loop:
 
 	block->accessed = TRUE;
 
+	mutex_exit(&block->mutex);
+
+	buf_block_make_young(block);
+
 #ifdef UNIV_DEBUG_FILE_ACCESSES
 	ut_a(block->file_page_was_freed == FALSE);
 #endif	
-	mutex_exit(&(buf_pool->mutex));
 
 #ifdef UNIV_DEBUG
 	buf_dbg_counter++;
@@ -1204,13 +1236,14 @@ loop:
 		}
 
 		if (!success) {
-			mutex_enter(&(buf_pool->mutex));
+			mutex_enter(&block->mutex);
 
 			block->buf_fix_count--;
+
+			mutex_exit(&block->mutex);
 #ifdef UNIV_SYNC_DEBUG
 			rw_lock_s_unlock(&(block->debug_latch));
 #endif			
-			mutex_exit(&(buf_pool->mutex));
 
 			return(NULL);
 		}
@@ -1221,18 +1254,16 @@ loop:
 			completes */
 
 		        for (;;) {
-			        mutex_enter(&(buf_pool->mutex));
+				mutex_enter(&block->mutex);
 
 		                if (block->io_fix == BUF_IO_READ) {
 
-				        mutex_exit(&(buf_pool->mutex));
+					mutex_exit(&block->mutex);
 				  
-				        /* Sleep 20 milliseconds */
-
-				        os_thread_sleep(20000);
+					os_thread_sleep(WAIT_FOR_READ);
 				} else {
 				  
-				       mutex_exit(&(buf_pool->mutex));
+					mutex_exit(&block->mutex);
 
 				       break;
 				}
@@ -1290,15 +1321,15 @@ buf_page_optimistic_get_func(
 
 	ut_ad(mtr && block);
 	ut_ad((rw_latch == RW_S_LATCH) || (rw_latch == RW_X_LATCH));
-	
-	mutex_enter(&(buf_pool->mutex));
 
 	/* If AWE is used, block may have a different frame now, e.g., NULL */
-	
+
+	mutex_enter(&block->mutex);
+
 	if (UNIV_UNLIKELY(block->state != BUF_BLOCK_FILE_PAGE)
-			|| UNIV_UNLIKELY(block->frame != guess)) {
-	exit_func:
-		mutex_exit(&(buf_pool->mutex));
+	    || UNIV_UNLIKELY(block->frame != guess)) {
+
+		mutex_exit(&block->mutex);
 
 		return(FALSE);
 	}
@@ -1308,15 +1339,14 @@ buf_page_optimistic_get_func(
 #else
 	buf_block_buf_fix_inc(block);
 #endif
-	buf_block_make_young(block);
-
-	/* Check if this is the first access to the page */
-
 	accessed = block->accessed;
-
 	block->accessed = TRUE;
 
-	mutex_exit(&(buf_pool->mutex));
+	mutex_exit(&block->mutex);
+
+	buf_block_make_young(block);
+
+	/* Check if this is the first access to the page */
 
 	ut_ad(!ibuf_inside() || ibuf_page(block->space, block->offset));
 
@@ -1331,13 +1361,16 @@ buf_page_optimistic_get_func(
 	}
 
 	if (UNIV_UNLIKELY(!success)) {
-		mutex_enter(&(buf_pool->mutex));
+		mutex_enter(&block->mutex);
 		
 		block->buf_fix_count--;
+
+		mutex_exit(&block->mutex);
+
 #ifdef UNIV_SYNC_DEBUG
 		rw_lock_s_unlock(&(block->debug_latch));
 #endif
-		goto exit_func;
+		return(FALSE);
 	}
 
 	if (UNIV_UNLIKELY(!UT_DULINT_EQ(modify_clock, block->modify_clock))) {
@@ -1350,13 +1383,16 @@ buf_page_optimistic_get_func(
 			rw_lock_x_unlock(&(block->lock));
 		}
 
-		mutex_enter(&(buf_pool->mutex));
+		mutex_enter(&block->mutex);
 		
 		block->buf_fix_count--;
+
+		mutex_exit(&block->mutex);
+
 #ifdef UNIV_SYNC_DEBUG
 		rw_lock_s_unlock(&(block->debug_latch));
 #endif
-		goto exit_func;
+		return(FALSE);
 	}
 
 	mtr_memo_push(mtr, block, fix_type);
@@ -1413,10 +1449,10 @@ buf_page_get_known_nowait(
 	ut_ad(mtr);
 	ut_ad((rw_latch == RW_S_LATCH) || (rw_latch == RW_X_LATCH));
 	
-	mutex_enter(&(buf_pool->mutex));
-
 	block = buf_block_align(guess);
 
+	mutex_enter(&block->mutex);
+
 	if (block->state == BUF_BLOCK_REMOVE_HASH) {
 	        /* Another thread is just freeing the block from the LRU list
 	        of the buffer pool: do not try to access this page; this
@@ -1425,7 +1461,7 @@ buf_page_get_known_nowait(
 		we have already removed it from the page address hash table
 		of the buffer pool. */
 
-	        mutex_exit(&(buf_pool->mutex));
+		mutex_exit(&block->mutex);
 
 		return(FALSE);
 	}
@@ -1437,12 +1473,12 @@ buf_page_get_known_nowait(
 #else
 	buf_block_buf_fix_inc(block);
 #endif
+	mutex_exit(&block->mutex);
+
 	if (mode == BUF_MAKE_YOUNG) {
 		buf_block_make_young(block);
 	}
 
-	mutex_exit(&(buf_pool->mutex));
-
 	ut_ad(!ibuf_inside() || (mode == BUF_KEEP_OLD));
 
 	if (rw_latch == RW_S_LATCH) {
@@ -1456,13 +1492,15 @@ buf_page_get_known_nowait(
 	}
 	
 	if (!success) {
-		mutex_enter(&(buf_pool->mutex));
+		mutex_enter(&block->mutex);
 		
 		block->buf_fix_count--;
+
+		mutex_exit(&block->mutex);
+
 #ifdef UNIV_SYNC_DEBUG
 		rw_lock_s_unlock(&(block->debug_latch));
 #endif		
-		mutex_exit(&(buf_pool->mutex));
 
 		return(FALSE);
 	}
@@ -1510,8 +1548,7 @@ buf_page_init_for_backup_restore(
 	block->offset 		= offset;
 
 	block->lock_hash_val	= 0;
-	block->lock_mutex	= NULL;
-	
+
 	block->freed_page_clock = 0;
 
 	block->newest_modification = ut_dulint_zero;
@@ -1543,6 +1580,7 @@ buf_page_init(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&(block->mutex)));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(block->state != BUF_BLOCK_FILE_PAGE);
 
@@ -1557,8 +1595,7 @@ buf_page_init(
 	block->index		= NULL;
 	
 	block->lock_hash_val	= lock_rec_hash(space, offset);
-	block->lock_mutex	= NULL;
-	
+
 	/* Insert into the hash table of file pages */
 
         if (buf_page_hash_get(space, offset)) {
@@ -1650,6 +1687,7 @@ buf_page_init_for_read(
 	ut_a(block);
 
 	mutex_enter(&(buf_pool->mutex));
+	mutex_enter(&block->mutex);
 
 	if (fil_tablespace_deleted_or_being_deleted_in_mem(space,
 							tablespace_version)) {
@@ -1662,7 +1700,9 @@ buf_page_init_for_read(
 		/* The page belongs to a space which has been deleted or is
 		being deleted, or the page is already in buf_pool, return */
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
+
 		buf_block_free(block);
 
 		if (mode == BUF_READ_IBUF_PAGES_ONLY) {
@@ -1682,6 +1722,7 @@ buf_page_init_for_read(
 	buf_LRU_add_block(block, TRUE); 	/* TRUE == to old blocks */
 	
 	block->io_fix = BUF_IO_READ;
+
 	buf_pool->n_pend_reads++;
 	
 	/* We set a pass-type x-lock on the frame because then the same
@@ -1693,6 +1734,7 @@ buf_page_init_for_read(
 	
 	rw_lock_x_lock_gen(&(block->lock), BUF_IO_READ);
 	
+	mutex_exit(&block->mutex);
  	mutex_exit(&(buf_pool->mutex));
 
 	if (mode == BUF_READ_IBUF_PAGES_ONLY) {
@@ -1757,6 +1799,8 @@ buf_page_create(
 
 	block = free_block;
 	
+	mutex_enter(&block->mutex);
+
 	buf_page_init(space, offset, block);
 
 	/* The block must be put to the LRU list */
@@ -1767,13 +1811,15 @@ buf_page_create(
 #else
 	buf_block_buf_fix_inc(block);
 #endif
+	buf_pool->n_pages_created++;
+
+	mutex_exit(&(buf_pool->mutex));
+
 	mtr_memo_push(mtr, block, MTR_MEMO_BUF_FIX);
 
 	block->accessed = TRUE;
 	
-	buf_pool->n_pages_created++;
-
-	mutex_exit(&(buf_pool->mutex));
+	mutex_exit(&block->mutex);
 
 	/* Delete possible entries for the page from the insert buffer:
 	such can exist if the page belonged to an index which was dropped */
@@ -1822,6 +1868,12 @@ buf_page_io_complete(
 
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
+	/* We do not need protect block->io_fix here by block->mutex to read
+	it because this is the only function where we can change the value
+	from BUF_IO_READ or BUF_IO_WRITE to some other value, and our code
+	ensures that this is the only thread that handles the i/o for this
+	block. */
+
 	io_type = block->io_fix;
 
 	if (io_type == BUF_IO_READ) {
@@ -1890,11 +1942,12 @@ buf_page_io_complete(
 		}
 	}
 	
+	mutex_enter(&(buf_pool->mutex));
+	mutex_enter(&block->mutex);
+
 #ifdef UNIV_IBUF_DEBUG
 	ut_a(ibuf_count_get(block->space, block->offset) == 0);
 #endif
-	mutex_enter(&(buf_pool->mutex));
-	
 	/* Because this thread which does the unlocking is not the same that
 	did the locking, we use a pass value != 0 in unlock, which simply
 	removes the newest lock debug record, without checking the thread
@@ -1937,6 +1990,7 @@ buf_page_io_complete(
 #endif /* UNIV_DEBUG */
 	}
 	
+	mutex_exit(&block->mutex);
 	mutex_exit(&(buf_pool->mutex));
 
 #ifdef UNIV_DEBUG
@@ -1999,6 +2053,8 @@ buf_validate(void)
 
 		block = buf_pool_get_nth_block(buf_pool, i);
 
+		mutex_enter(&block->mutex);
+
 		if (block->state == BUF_BLOCK_FILE_PAGE) {
 
 			ut_a(buf_page_hash_get(block->space,
@@ -2042,6 +2098,8 @@ buf_validate(void)
 		} else if (block->state == BUF_BLOCK_NOT_USED) {
 			n_free++;
 		}
+
+		mutex_exit(&block->mutex);
  	}
 
 	if (n_lru + n_free > buf_pool->curr_size) {
@@ -2185,11 +2243,17 @@ buf_get_latched_pages_number(void)
 
         for (i = 0; i < buf_pool->curr_size; i++) {
 
-               block = buf_pool_get_nth_block(buf_pool, i);
+		block = buf_pool_get_nth_block(buf_pool, i);
+
+		if (block->magic_n == BUF_BLOCK_MAGIC_N) {
+			mutex_enter(&block->mutex);
 
-               if (((block->buf_fix_count != 0) || (block->io_fix != 0)) &&
-                    block->magic_n == BUF_BLOCK_MAGIC_N )
-                       fixed_pages_number++;
+			if (block->buf_fix_count != 0 || block->io_fix != 0) {
+				fixed_pages_number++;
+			}
+
+			mutex_exit(&block->mutex);
+		}
         }
 
         mutex_exit(&(buf_pool->mutex));
@@ -2354,16 +2418,21 @@ buf_all_freed(void)
 
 		block = buf_pool_get_nth_block(buf_pool, i);
 
+		mutex_enter(&block->mutex);
+
 		if (block->state == BUF_BLOCK_FILE_PAGE) {
 
 			if (!buf_flush_ready_for_replace(block)) {
 
 				fprintf(stderr,
 					"Page %lu %lu still fixed or dirty\n",
-					(ulong) block->space, (ulong) block->offset);
+					(ulong) block->space,
+					(ulong) block->offset);
 			    	ut_error;
 			}
 		}
+
+		mutex_exit(&block->mutex);
  	}
 
 	mutex_exit(&(buf_pool->mutex));
diff --git a/innobase/buf/buf0flu.c b/innobase/buf/buf0flu.c
index e39d1ae0a71..fc7b60bf5fb 100644
--- a/innobase/buf/buf0flu.c
+++ b/innobase/buf/buf0flu.c
@@ -114,6 +114,7 @@ buf_flush_ready_for_replace(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	if (block->state != BUF_BLOCK_FILE_PAGE) {
 		ut_print_timestamp(stderr);
@@ -148,6 +149,7 @@ buf_flush_ready_for_flush(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&(block->mutex)));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
@@ -539,8 +541,15 @@ buf_flush_try_page(
 
 	ut_a(!block || block->state == BUF_BLOCK_FILE_PAGE);
 
+	if (!block) {
+		mutex_exit(&(buf_pool->mutex));
+		return(0);
+	}
+
+	mutex_enter(&block->mutex);
+
 	if (flush_type == BUF_FLUSH_LIST
-	    && block && buf_flush_ready_for_flush(block, flush_type)) {
+	    && buf_flush_ready_for_flush(block, flush_type)) {
 	
 		block->io_fix = BUF_IO_WRITE;
 
@@ -578,6 +587,7 @@ buf_flush_try_page(
 			locked = TRUE;
 		}
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		if (!locked) {
@@ -598,8 +608,8 @@ buf_flush_try_page(
 		
 		return(1);
 
-	} else if (flush_type == BUF_FLUSH_LRU && block
-			&& buf_flush_ready_for_flush(block, flush_type)) {
+	} else if (flush_type == BUF_FLUSH_LRU
+		   && buf_flush_ready_for_flush(block, flush_type)) {
 
 		/* VERY IMPORTANT:
 		Because any thread may call the LRU flush, even when owning
@@ -639,14 +649,15 @@ buf_flush_try_page(
 		buf_pool mutex: this ensures that the latch is acquired
 		immediately. */
 		
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		buf_flush_write_block_low(block);
 
 		return(1);
 
-	} else if (flush_type == BUF_FLUSH_SINGLE_PAGE && block
-			&& buf_flush_ready_for_flush(block, flush_type)) {
+	} else if (flush_type == BUF_FLUSH_SINGLE_PAGE
+		   && buf_flush_ready_for_flush(block, flush_type)) {
 	
 		block->io_fix = BUF_IO_WRITE;
 
@@ -672,6 +683,7 @@ buf_flush_try_page(
 
 		(buf_pool->n_flush[flush_type])++;
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		rw_lock_s_lock_gen(&(block->lock), BUF_IO_WRITE);
@@ -688,11 +700,12 @@ buf_flush_try_page(
 		buf_flush_write_block_low(block);
 		
 		return(1);
-	} else {
-		mutex_exit(&(buf_pool->mutex));
+	}
 
-		return(0);
-	}		
+	mutex_exit(&block->mutex);
+	mutex_exit(&(buf_pool->mutex));
+
+	return(0);
 }
 
 /***************************************************************
@@ -737,34 +750,48 @@ buf_flush_try_neighbors(
 		block = buf_page_hash_get(space, i);
 		ut_a(!block || block->state == BUF_BLOCK_FILE_PAGE);
 
-		if (block && flush_type == BUF_FLUSH_LRU && i != offset
-		    && !block->old) {
+		if (!block) {
+
+			continue;
+
+		} else if (flush_type == BUF_FLUSH_LRU && i != offset
+			   && !block->old) {
 
 		        /* We avoid flushing 'non-old' blocks in an LRU flush,
 		        because the flushed blocks are soon freed */
 
 		        continue;
-		}
+		} else {
+
+			mutex_enter(&block->mutex);
+
+			if (buf_flush_ready_for_flush(block, flush_type)
+			    && (i == offset || block->buf_fix_count == 0)) {
+				/* We only try to flush those
+				neighbors != offset where the buf fix count is
+				zero, as we then know that we probably can
+				latch the page without a semaphore wait.
+				Semaphore waits are expensive because we must
+				flush the doublewrite buffer before we start
+				waiting. */
 
-		if (block && buf_flush_ready_for_flush(block, flush_type)
-		   && (i == offset || block->buf_fix_count == 0)) {
-			/* We only try to flush those neighbors != offset
-			where the buf fix count is zero, as we then know that
-			we probably can latch the page without a semaphore
-			wait. Semaphore waits are expensive because we must
-			flush the doublewrite buffer before we start
-			waiting. */
+				mutex_exit(&block->mutex);
 
-			mutex_exit(&(buf_pool->mutex));
+				mutex_exit(&(buf_pool->mutex));
 
-			/* Note: as we release the buf_pool mutex above, in
-			buf_flush_try_page we cannot be sure the page is still
-			in a flushable state: therefore we check it again
-			inside that function. */
+				/* Note: as we release the buf_pool mutex
+				above, in buf_flush_try_page we cannot be sure
+				the page is still in a flushable state:
+				therefore we check it again inside that
+				function. */
 
-			count += buf_flush_try_page(space, i, flush_type);
+				count += buf_flush_try_page(space, i,
+							    flush_type);
 
-			mutex_enter(&(buf_pool->mutex));
+				mutex_enter(&(buf_pool->mutex));
+			} else {
+				mutex_exit(&block->mutex);
+			}
 		}
 	}
 				
@@ -858,12 +885,15 @@ buf_flush_batch(
 	    	while ((block != NULL) && !found) {
 			ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
+			mutex_enter(&block->mutex);
+
 			if (buf_flush_ready_for_flush(block, flush_type)) {
 
 				found = TRUE;
 				space = block->space;
 				offset = block->offset;
 	    
+				mutex_exit(&block->mutex);
 				mutex_exit(&(buf_pool->mutex));
 
 				old_page_count = page_count;
@@ -881,10 +911,14 @@ buf_flush_batch(
 
 			} else if (flush_type == BUF_FLUSH_LRU) {
 
+				mutex_exit(&block->mutex);
+
 				block = UT_LIST_GET_PREV(LRU, block);
 			} else {
 				ut_ad(flush_type == BUF_FLUSH_LIST);
 
+				mutex_exit(&block->mutex);
+
 				block = UT_LIST_GET_PREV(flush_list, block);
 			}
 	    	}
@@ -966,10 +1000,14 @@ buf_flush_LRU_recommendation(void)
 	       				+ BUF_FLUSH_EXTRA_MARGIN)
 	       && (distance < BUF_LRU_FREE_SEARCH_LEN)) {
 
+		mutex_enter(&block->mutex);
+
 		if (buf_flush_ready_for_replace(block)) {
 			n_replaceable++;
 		}
 
+		mutex_exit(&block->mutex);
+
 		distance++;
 			
 		block = UT_LIST_GET_PREV(LRU, block);
diff --git a/innobase/buf/buf0lru.c b/innobase/buf/buf0lru.c
index 8b135cc5db3..dfee2add045 100644
--- a/innobase/buf/buf0lru.c
+++ b/innobase/buf/buf0lru.c
@@ -86,6 +86,9 @@ scan_again:
 	block = UT_LIST_GET_LAST(buf_pool->LRU);
 
 	while (block != NULL) {
+
+		mutex_enter(&block->mutex);
+
 	        ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
 		if (block->space == id
@@ -112,6 +115,8 @@ scan_again:
 			if (block->is_hashed) {
 				page_no = block->offset;
 			
+				mutex_exit(&block->mutex);
+
 				mutex_exit(&(buf_pool->mutex));
 
 				/* Note that the following call will acquire
@@ -138,6 +143,7 @@ scan_again:
 			buf_LRU_block_free_hashed_page(block);
 		}
 next_page:
+		mutex_exit(&block->mutex);
 		block = UT_LIST_GET_PREV(LRU, block);
 	}
 
@@ -211,6 +217,9 @@ buf_LRU_search_and_free_block(
 
 	while (block != NULL) {
 	        ut_a(block->in_LRU_list);
+
+		mutex_enter(&block->mutex);
+
 		if (buf_flush_ready_for_replace(block)) {
 
 #ifdef UNIV_DEBUG
@@ -225,6 +234,7 @@ buf_LRU_search_and_free_block(
 			buf_LRU_block_remove_hashed_page(block);
 
 			mutex_exit(&(buf_pool->mutex));
+			mutex_exit(&block->mutex);
 
 			/* Remove possible adaptive hash index built on the
 			page; in the case of AWE the block may not have a
@@ -233,15 +243,21 @@ buf_LRU_search_and_free_block(
 			if (block->frame) {
 				btr_search_drop_page_hash_index(block->frame);
 			}
-			mutex_enter(&(buf_pool->mutex));
 
 			ut_a(block->buf_fix_count == 0);
 
+			mutex_enter(&(buf_pool->mutex));
+			mutex_enter(&block->mutex);
+
 			buf_LRU_block_free_hashed_page(block);
 			freed = TRUE;
+			mutex_exit(&block->mutex);
 
 			break;
 		}
+
+		mutex_exit(&block->mutex);
+
 		block = UT_LIST_GET_PREV(LRU, block);
 		distance++;
 
@@ -415,8 +431,12 @@ loop:
 			}
 		}
 		
+		mutex_enter(&block->mutex);
+
 		block->state = BUF_BLOCK_READY_FOR_USE;
 
+		mutex_exit(&block->mutex);
+
 		mutex_exit(&(buf_pool->mutex));
 
 		if (started_monitor) {
@@ -818,6 +838,7 @@ buf_LRU_block_free_non_file_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_ad(block);
 	
@@ -857,6 +878,7 @@ buf_LRU_block_remove_hashed_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_ad(block);
 	
@@ -914,6 +936,7 @@ buf_LRU_block_free_hashed_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(block->state == BUF_BLOCK_REMOVE_HASH);