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Fix for BUG#39210 "Maria deadlock in _ma_bitmap_wait_or_flush". It was a thread

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which nobody woke up (see comment of ma_bitmap.c). No testcase, this requires
multiple threads and is automatically tested at push time by maria_stress.yy (pushbuild2).

storage/maria/ma_bitmap.c:
  * _ma_bitmap_wait_or_flush() didn't publish that it was waiting for bitmap to not
  be over-allocated (i.e. didn't modify bitmap->flush_all_requested) so nobody
  (_ma_bitmap_flushable(), _ma_bitmap_release_unused()) knew it had to wake it up
  => it stalled (BUG#39210). In fact the wait in _ma_bitmap_wait_or_flush()
  is not needed, it's ok if this function sends the over-allocated bitmap to page
  cache and keeps pin on it (_ma_bitmap_unpin_all() will unpin it later, and
  the one who added _ma_bitmap_wait_or_flush() didn't know it). Function
  is thus deleted, as _ma_bitmap_flush() can do its job.
  * After fixing that, test runs longer and BUG 39665 happens, which looks like
  a separate page cache bug.
  * Smaller changes: _ma_bitmap_flush_all() called write_changed_bitmap() even
  though it might not be changed; added some DBUG calls in functions; split
  assertions.
  * In _ma_bitmap_release_unused(), it's more logical to test non_flushable_state
  than now_transactional to know if we have to decrement non_flushable
  (it's exactly per the definition of non_flushable_state).
storage/maria/ma_blockrec.c:
  _ma_bitmap_wait_or_flush() is not needed.
  ******
  new prototype and splitting assertion in three (3rd one fires: BUG 39665)
storage/maria/ma_blockrec.h:
  _ma_bitmap_wait_or_flush() is not needed.
This commit is contained in:
Guilhem Bichot
2008-10-14 11:38:07 +02:00
parent 058916ae02
commit ed567bd2a9
3 changed files with 34 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

74
storage/maria/ma_bitmap.c
View File

@@ -281,6 +281,14 @@ my_bool _ma_bitmap_end(MARIA_SHARE *share)
by this thread (ie, checking the changed flag is ok). The reason we
check it again in the mutex is that if someone else did a flush at the
same time, we don't have to do the write.
This is also ok for _ma_scan_init_block_record() which does not want to
miss rows: it cares only for committed rows, that is, rows for which there
was a commit before our transaction started; as commit and transaction's
start are protected by the same LOCK_trn_list mutex, we see memory at
least as new as at other transaction's commit time, so if the committed
rows caused bitmap->changed to be true, we see it; if we see 0 it really
means a flush happened since then. So, it's ok to read without bitmap's
mutex.
RETURN
0 ok
@@ -305,38 +313,6 @@ my_bool _ma_bitmap_flush(MARIA_SHARE *share)
}
/*
@brief Send updated bitmap to the page cache if bitmap is free
@note
This is used by reader threads which don't unpin things
*/
my_bool _ma_bitmap_wait_or_flush(MARIA_SHARE *share)
{
my_bool res= 0;
MARIA_FILE_BITMAP *bitmap= &share->bitmap;
DBUG_ENTER("_ma_bitmap_flush");
if (bitmap->changed)
{
pthread_mutex_lock(&bitmap->bitmap_lock);
while (bitmap->non_flushable && bitmap->changed)
{
DBUG_PRINT("info", ("waiting for bitmap to be flushable"));
pthread_cond_wait(&bitmap->bitmap_cond, &bitmap->bitmap_lock);
}
if (bitmap->changed)
{
bitmap->changed= 0;
res= write_changed_bitmap(share, bitmap);
}
pthread_mutex_unlock(&bitmap->bitmap_lock);
}
DBUG_RETURN(res);
}
/**
Dirty-page filtering criteria for bitmap pages
@@ -386,8 +362,11 @@ my_bool _ma_bitmap_flush_all(MARIA_SHARE *share)
unpinned. We keep the mutex to preserve this situation, and flush to the
file.
*/
res= write_changed_bitmap(share, bitmap);
bitmap->changed= FALSE;
if (bitmap->changed)
{
res= write_changed_bitmap(share, bitmap);
bitmap->changed= FALSE;
}
/*
We do NOT use FLUSH_KEEP_LAZY because we must be sure that bitmap
pages have been flushed. That's a condition of correctness of
@@ -424,6 +403,8 @@ my_bool _ma_bitmap_flush_all(MARIA_SHARE *share)
@return Operation status
@retval 0 ok
@note This unpins pages pinned by other threads.
*/
static void _ma_bitmap_unpin_all(MARIA_SHARE *share)
@@ -2139,8 +2120,8 @@ my_bool _ma_bitmap_set_full_page_bits(MARIA_HA *info,
function first waits for the flush to be done.
@note
info->non_flushable_state is set to 1 if we have incremented
bitmap->info->non_flushable and not yet decremented it.
this sets info->non_flushable_state to 1 if we have incremented
bitmap->non_flushable and not yet decremented it.
@param share Table's share
@param non_flushable_inc Increment of MARIA_FILE_BITMAP::non_flushable
@@ -2151,20 +2132,21 @@ void _ma_bitmap_flushable(MARIA_HA *info, int non_flushable_inc)
{
MARIA_SHARE *share= info->s;
MARIA_FILE_BITMAP *bitmap;
DBUG_ENTER("_ma_bitmap_flushable");
/*
Not transactional tables are never automaticly flushed and needs no
protection
*/
if (!share->now_transactional)
return;
DBUG_VOID_RETURN;
bitmap= &share->bitmap;
if (non_flushable_inc == -1)
{
pthread_mutex_lock(&bitmap->bitmap_lock);
DBUG_ASSERT((int) bitmap->non_flushable > 0 &&
info->non_flushable_state == 1);
DBUG_ASSERT((int) bitmap->non_flushable > 0);
DBUG_ASSERT(info->non_flushable_state == 1);
info->non_flushable_state= 0;
if (--bitmap->non_flushable == 0)
{
@@ -2182,14 +2164,15 @@ void _ma_bitmap_flushable(MARIA_HA *info, int non_flushable_inc)
}
DBUG_PRINT("info", ("bitmap->non_flushable: %u", bitmap->non_flushable));
pthread_mutex_unlock(&bitmap->bitmap_lock);
return;
DBUG_VOID_RETURN;
}
DBUG_ASSERT(non_flushable_inc == 1 && info->non_flushable_state == 0);
DBUG_ASSERT(non_flushable_inc == 1);
DBUG_ASSERT(info->non_flushable_state == 0);
/* It is a read without mutex because only an optimization */
if (unlikely(bitmap->flush_all_requested))
{
/*
_ma_bitmap_flush_all() is waiting for the bitmap to become
Some other thread is waiting for the bitmap to become
flushable. Not the moment to make the bitmap unflushable or more
unflushable; let's rather back off and wait. If we didn't do this, with
multiple writers, there may always be one thread causing the bitmap to
@@ -2214,6 +2197,7 @@ void _ma_bitmap_flushable(MARIA_HA *info, int non_flushable_inc)
bitmap->non_flushable++;
info->non_flushable_state= 1;
DBUG_PRINT("info", ("bitmap->non_flushable: %u", bitmap->non_flushable));
DBUG_VOID_RETURN;
}
@@ -2321,10 +2305,10 @@ my_bool _ma_bitmap_release_unused(MARIA_HA *info, MARIA_BITMAP_BLOCKS *blocks)
goto err;
}
if (info->s->now_transactional)
/* This duplicates ma_bitmap_flushable(-1) except it already has mutex */
if (info->non_flushable_state)
{
DBUG_ASSERT((int) bitmap->non_flushable >= 0 &&
info->non_flushable_state);
DBUG_ASSERT((int) bitmap->non_flushable >= 0);
info->non_flushable_state= 0;
if (--bitmap->non_flushable == 0)
{