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Bug#20422680 BUF_POOL_WATCH_SET WOULD CRASH TRYING

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TO USE A SECOND WATCH PAGE PER INSTANCE

Description:
	BUF_POOL_WATCH_SIZE is also initialized to number of purge threads.
so BUF_POOL_WATCH_SIZE will never be lesser than number of purge threads.
From the code, there is no scope for purge thread to skip buf_pool_watch_unset.
So there can be at most one buffer pool watch active per purge thread.
In other words, there is no chance for purge thread instance to hold a watch
when setting another watch.

Solution:
	Adding code comments to clarify the issue.

Reviewed-by: Marko Mäkelä <marko.makela@oracle.com>
Approved via Bug page.
This commit is contained in:
Thirunarayanan Balathandayuthapani 2015-03-24 14:09:18 +05:30
parent 26e845c19d
commit f8eacccf2a
1 changed files with 4 additions and 1 deletions
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5
storage/innobase/buf/buf0buf.c
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@ -1,6 +1,6 @@
/*****************************************************************************
Copyright (c) 1995, 2014, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2008, Google Inc.
Portions of this file contain modifications contributed and copyrighted by
@ -1528,6 +1528,9 @@ buf_pool_watch_set(
return(NULL);
}
/* The maximum number of purge threads should never exceed
BUF_POOL_WATCH_SIZE. So there is no way for purge thread
instance to hold a watch when setting another watch. */
for (i = 0; i < BUF_POOL_WATCH_SIZE; i++) {
bpage = &buf_pool->watch[i];