On Wed, Jul 10, 2024 at 04:19:53PM +0206, John Ogness wrote: > On 2024-07-10, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > console_lock is the outermost subsystem lock for a lot of subsystems, > > which means get/put_user must nest within. Which means it cannot be > > acquired somewhere deeply nested in other locks, and most definitely > > not while holding fs locks potentially needed to resolve faults. > > > > console_trylock is the best we can do here. But John pointed out on a > > previous version that this is futile: > > > > "Using the console lock here at all is wrong. The console lock does not > > prevent other CPUs from calling printk() and inserting lines in between. > > > > "There is no way to guarantee a contiguous ringbuffer block using > > multiple printk() calls. > > > > "The console_lock usage should be removed." > > > > https://lore.kernel.org/lkml/87frsh33xp.fsf@xxxxxxxxxxxxxxxxxxxxx/ > > > > Do that. > > Note that there is more of this incorrect usage of console lock in: > > fs/bcachefs/debug.c:bch2_btree_verify_replica() > > fs/bcachefs/bset.c:bch2_dump_btree_node() > > from commit 1c6fdbd8f246("bcachefs: Initial commit") > > ... and its parent bcache: > > drivers/md/bcache/debug.c:bch_btree_verify() > > drivers/md/bcache/bset.c:bch_dump_bucket() > > from commit cafe56359144("bcache: A block layer cache") > > These should also be removed. Although Kent should verify that the > console lock is not providing some sort of necessary side-effect > synchronization. I'll take a look, at least some of them seem doable to audit without deep bcachefs understanding. Thanks for pointing them out, I should have looked a bit more at git grep ... -Sima -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
