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[Laurynas Biveinis <laurynas.biveinis@xxxxxxxxx>]

Public bug reported:

Copy of http://bugs.mysql.com/bug.php?id=75503:

[14 Jan 11:27] Laurynas Biveinis
Description:
Each buffer pool instance has an array watch[] of buf_page_t. They are BUF_BLOCK_ZIP_PAGE when free and BUF_BLOCK_POOL_WATCH when used as a set watch sentinel.

Then we have the following code in buf_pool_watch_set:
...
	for (i = 0; i < BUF_POOL_WATCH_SIZE; i++) {
		bpage = &buf_pool->watch[i];
...
		switch (bpage->state) {
		case BUF_BLOCK_POOL_WATCH:
/* set watch */
			return(NULL);
		case BUF_BLOCK_ZIP_PAGE:
...
			break;
...
		}
	}
...
	ut_error;

Which shows that buf_pool_watch_set should crash when trying to set a
watch on an instance with one watch already set.

How to repeat:
Code reading. Maybe some workload with innodb_buffer_pool_instances=1 innodb_purge_threads=32.

Suggested fix:
Looks like a typo: s/break/continue

** Affects: mysql-server
     Importance: Unknown
         Status: Unknown

** Affects: percona-server
     Importance: High
         Status: Triaged

** Affects: percona-server/5.1
     Importance: High
         Status: Triaged

** Affects: percona-server/5.5
     Importance: High
         Status: Triaged

** Affects: percona-server/5.6
     Importance: High
         Status: Triaged

** Affects: percona-server/5.7
     Importance: High
     Assignee: Laurynas Biveinis (laurynas-biveinis)
         Status: In Progress


** Tags: innodb upstream

** Also affects: percona-server/5.7
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.6
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.1
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.5
   Importance: Undecided
       Status: New

** Changed in: percona-server/5.7
     Assignee: (unassigned) => Laurynas Biveinis (laurynas-biveinis)

** Changed in: percona-server/5.7
   Importance: Undecided => High

** Changed in: percona-server/5.6
   Importance: Undecided => High

** Changed in: percona-server/5.5
   Importance: Undecided => High

** Changed in: percona-server/5.1
   Importance: Undecided => High

** Changed in: percona-server/5.1
       Status: New => Triaged

** Changed in: percona-server/5.5
       Status: New => Triaged

** Changed in: percona-server/5.6
       Status: New => Triaged

** Changed in: percona-server/5.7
       Status: New => In Progress

** Tags added: innodb upstream

** Bug watch added: MySQL Bug System #75503
   http://bugs.mysql.com/bug.php?id=75503

** Also affects: mysql-server via
   http://bugs.mysql.com/bug.php?id=75503
   Importance: Unknown
       Status: Unknown

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https://bugs.launchpad.net/bugs/1411692

Title:
  buf_pool_watch_set would crash trying to use a second watch page per
  instance?

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