From 10c92bd7ac995f385c231f4db1564e1e6411f469 Mon Sep 17 00:00:00 2001
From: marko <>
Date: Tue, 9 Jan 2007 12:39:50 +0000
Subject: [PATCH] branches/zip: buf_buddy_alloc_clean(): Restart the scan after
 a successful buf_LRU_free_block().

buf_LRU_free_block(): Note that buf_pool->mutex may be temporarily released.
---
 buf/buf0buddy.c   | 14 ++++++++++++++
 buf/buf0lru.c     |  7 ++++++-
 include/buf0lru.h |  7 ++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/buf/buf0buddy.c b/buf/buf0buddy.c
index 59a1d4146cc..eb0ea680507 100644
--- a/buf/buf0buddy.c
+++ b/buf/buf0buddy.c
@@ -234,6 +234,7 @@ buf_buddy_alloc_clean(
 	/* Free blocks from the end of the LRU list until enough space
 	is available. */
 
+free_LRU:
 	for (bpage = UT_LIST_GET_LAST(buf_pool->LRU); bpage;
 	     bpage = UT_LIST_GET_PREV(LRU, bpage)) {
 
@@ -258,6 +259,9 @@ buf_buddy_alloc_clean(
 
 		mutex_exit(block_mutex);
 
+		/* The block was successfully freed.
+		Attempt to allocate memory. */
+
 		if (i < BUF_BUDDY_SIZES) {
 
 			ret = buf_buddy_alloc_zip(i);
@@ -274,6 +278,16 @@ buf_buddy_alloc_clean(
 				return(block->frame);
 			}
 		}
+
+		/* A successful buf_LRU_free_block() may release and
+		reacquire buf_pool->mutex, and thus bpage->LRU of
+		an uncompressed page may point to garbage.  Furthermore,
+		if bpage were a compressed page descriptor, it would
+		have been deallocated by buf_LRU_free_block().
+
+		Thus, we must restart the traversal of the LRU list. */
+
+		goto free_LRU;
 	}
 
 	return(NULL);
diff --git a/buf/buf0lru.c b/buf/buf0lru.c
index a6e8fc9afce..beb7358b13f 100644
--- a/buf/buf0lru.c
+++ b/buf/buf0lru.c
@@ -878,7 +878,12 @@ Try to free a block. */
 ibool
 buf_LRU_free_block(
 /*===============*/
-				/* out: TRUE if freed */
+				/* out: TRUE if freed.  If bpage is a
+				descriptor of a compressed-only page,
+				the descriptor object will be freed
+				as well.  If this function returns FALSE,
+				it will not temporarily release
+				buf_pool->mutex. */
 	buf_page_t*	bpage,	/* in: block to be freed */
 	ibool		zip)	/* in: TRUE if should remove also the
 				compressed page of an uncompressed page */
diff --git a/include/buf0lru.h b/include/buf0lru.h
index a0c1b16ca57..f6a1e1a3d2c 100644
--- a/include/buf0lru.h
+++ b/include/buf0lru.h
@@ -78,7 +78,12 @@ Try to free a block. */
 ibool
 buf_LRU_free_block(
 /*===============*/
-				/* out: TRUE if freed */
+				/* out: TRUE if freed.  If bpage is a
+				descriptor of a compressed-only page,
+				the descriptor object will be freed
+				as well.  If this function returns FALSE,
+				it will not temporarily release
+				buf_pool->mutex. */
 	buf_page_t*	block,	/* in: block to be freed */
 	ibool		zip);	/* in: TRUE if should remove also the
 				compressed page of an uncompressed page */