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MDEV-10104 Table lock race condition with replication

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Problem was two race condtion in Aria page cache:
- find_block() didn't inform free_block() that it had released requests
- free_block() didn't handle pinned blocks, which could happen if
  free_block() was called as part of flush. This is fixed by not freeing
  blocks that are pinned.  This is safe as when maria_close() is called
  when last thread is using a table, there can be no pinned blocks. For
  other flush calls it's safe to ignore pinned blocks.
This commit is contained in:
Monty 2017-05-05 13:08:23 +03:00
parent e3521ab904
commit fc25437aff
1 changed files with 46 additions and 13 deletions
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59
storage/maria/ma_pagecache.c
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@ -493,7 +493,8 @@ error:
#define FLUSH_CACHE 2000 /* sort this many blocks at once */
static void free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block);
static my_bool free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block,
my_bool abort_if_pinned);
static void unlink_hash(PAGECACHE *pagecache, PAGECACHE_HASH_LINK *hash_link);
#ifndef DBUG_OFF
static void test_key_cache(PAGECACHE *pagecache,
@ -1939,7 +1940,7 @@ restart:
removed from the cache as we set the PCBLOCK_REASSIGNED
flag (see the code below that handles reading requests).
*/
free_block(pagecache, block);
free_block(pagecache, block, 0);
return 0;
}
/* Wait until the page is flushed on disk */
@ -1950,7 +1951,7 @@ restart:
/* Invalidate page in the block if it has not been done yet */
DBUG_ASSERT(block->status); /* Should always be true */
if (block->status)
free_block(pagecache, block);
free_block(pagecache, block, 0);
return 0;
}
@ -1975,8 +1976,13 @@ restart:
}
else
{
DBUG_ASSERT(hash_link->requests > 0);
hash_link->requests--;
/*
When we come here either PCBLOCK_REASSIGNED or PCBLOCK_IN_SWITCH are
active. In both cases wqueue_release_queue() is called when the
state changes.
*/
DBUG_ASSERT(block->hash_link == hash_link);
remove_reader(block);
KEYCACHE_DBUG_PRINT("find_block",
("request waiting for old page to be saved"));
{
@ -3635,7 +3641,7 @@ static my_bool pagecache_delete_internal(PAGECACHE *pagecache,
DBUG_ASSERT(block->hash_link->requests > 0);
page_link->requests--;
/* See NOTE for pagecache_unlock() about registering requests. */
free_block(pagecache, block);
free_block(pagecache, block, 0);
dec_counter_for_resize_op(pagecache);
return 0;
@ -4227,7 +4233,8 @@ end:
and add it to the free list.
*/
static void free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block)
static my_bool free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block,
my_bool abort_if_pinned)
{
uint status= block->status;
KEYCACHE_THREAD_TRACE("free block");
@ -4241,11 +4248,27 @@ static void free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block)
/*
While waiting for readers to finish, new readers might request the
block. But since we set block->status|= PCBLOCK_REASSIGNED, they
will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled
will wait on block->wqueue[COND_FOR_SAVED]. They must be signaled
later.
*/
block->status|= PCBLOCK_REASSIGNED;
wait_for_readers(pagecache, block);
if (unlikely(abort_if_pinned) && unlikely(block->pins))
{
/*
Block got pinned while waiting for readers.
This can only happens when called from flush_pagecache_blocks_int()
when flushing blocks as part of prepare for maria_close() or from
flush_cached_blocks()
*/
block->status&= ~PCBLOCK_REASSIGNED;
unreg_request(pagecache, block, 0);
/* All pending requests for this page must be resubmitted. */
if (block->wqueue[COND_FOR_SAVED].last_thread)
wqueue_release_queue(&block->wqueue[COND_FOR_SAVED]);
return 1;
}
unlink_hash(pagecache, block->hash_link);
}
@ -4296,6 +4319,8 @@ static void free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block)
/* All pending requests for this page must be resubmitted. */
if (block->wqueue[COND_FOR_SAVED].last_thread)
wqueue_release_queue(&block->wqueue[COND_FOR_SAVED]);
return 0;
}
@ -4431,9 +4456,16 @@ static int flush_cached_blocks(PAGECACHE *pagecache,
if (! (type == FLUSH_KEEP || type == FLUSH_KEEP_LAZY ||
type == FLUSH_FORCE_WRITE))
{
pagecache->blocks_changed--;
pagecache->global_blocks_changed--;
free_block(pagecache, block);
if (!free_block(pagecache, block, 1))
{
pagecache->blocks_changed--;
pagecache->global_blocks_changed--;
}
else
{
block->status&= ~PCBLOCK_IN_FLUSH;
link_to_file_list(pagecache, block, file, 1);
}
}
else
{
@ -4671,7 +4703,7 @@ restart:
/* It's a temporary file */
pagecache->blocks_changed--;
pagecache->global_blocks_changed--;
free_block(pagecache, block);
free_block(pagecache, block, 0);
}
}
else if (type != FLUSH_KEEP_LAZY)
@ -4741,11 +4773,12 @@ restart:
#endif
next= block->next_changed;
if (block->hash_link->file.file == file->file &&
!block->pins &&
(! (block->status & PCBLOCK_CHANGED)
|| type == FLUSH_IGNORE_CHANGED))
{
reg_requests(pagecache, block, 1);
free_block(pagecache, block);
free_block(pagecache, block, 1);
}
}
}