The function ibuf_remove_free_page() was waiting for ibuf_mutex
while holding ibuf.index->lock. This constitutes a lock order
inversion and may cause InnoDB to hang when innodb_change_buffering
is enabled and ibuf_merge_or_delete_for_page() is being executed
concurrently.
In fact, there is no need for ibuf_remove_free_page() to reacquire
ibuf_mutex if we make ibuf.seg_size and ibuf.free_list_len
protected by the ibuf.index->lock as well as the root page latch rather
than by ibuf_mutex.
ibuf.seg_size, ibuf.free_list_len: Instead of ibuf_mutex, let the
ibuf.index->lock and the root page latch protect these, like ibuf.empty.
ibuf_init_at_db_start(): Acquire the root page latch before updating
ibuf.seg_size. (The ibuf.index would be created later.)
ibuf_data_enough_free_for_insert(), ibuf_data_too_much_free():
Assert also ibuf.index->lock.have_u_or_x().
ibuf_remove_free_page(): Acquire the ibuf.index->lock and the root page
latch before accessing ibuf.free_list_len. Simplify the way how the
root page latch is released and reacquired. Acquire and release
ibuf_mutex only once.
ibuf_free_excess_pages(), ibuf_insert_low(): Acquire also ibuf.index->lock
before reading ibuf.free_list_len.
ibuf_print(): Acquire ibuf.index->lock before reading
ibuf.free_list_len and ibuf.seg_size.
Reviewed by: Vladislav Lesin
Tested by: Matthias Leich
16d91f87ff