On Wed, 19 Jan 2022 20:34:17 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote: > Lockdep noticed that there is chance for a deadlock if we have > concurrent mmap, concurrent read, and the addition/removal of a > callback. > > As nicely explained by Boqun: > > " > Lockdep warned about the above sequences because rw_semaphore is a fair > read-write lock, and the following can cause a deadlock: > > TASK 1 TASK 2 TASK 3 > ====== ====== ====== > down_write(mmap_lock); > down_read(vmcore_cb_rwsem) > down_write(vmcore_cb_rwsem); // blocked > down_read(vmcore_cb_rwsem); // cannot get the lock because of the fairness > down_read(mmap_lock); // blocked I'm wondering about cc:stable. It's hard to believe that this is likely to be observed in real life. But the ongoing reports of lockdep splats will be irritating.
