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. John Ogness
