mariadb/storage/innobase/ibuf
Marko Mäkelä a2ee2c7ea1 MDEV-29930 Lock order inversion in ibuf_remove_free_page()
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
2025-09-11 13:25:08 +03:00
..
ibuf0ibuf.cc MDEV-29930 Lock order inversion in ibuf_remove_free_page() 2025-09-11 13:25:08 +03:00