On Wed, Feb 28, 2024 at 02:14:44PM -0500, Waiman Long wrote: > When some error conditions happen (like OOM), some kmemleak functions > call printk() to dump out some useful debugging information while holding > the kmemleak_lock. This may cause deadlock as the printk() function > may need to allocate additional memory leading to a create_object() > call acquiring kmemleak_lock again. > > Fix this deadlock issue by making sure that printk() is only called > after releasing the kmemleak_lock. I can't say I'm familiar with the printk() code but I always thought it uses some ring buffers as it can be called from all kind of contexts and allocation is not guaranteed. If printk() ends up taking kmemleak_lock through the slab allocator, I wonder whether we have bigger problems. The lock order is always kmemleak_lock -> object->lock but if printk() triggers a callback into kmemleak, we can also get object->lock -> kmemleak_lock ordering, so another potential deadlock. -- Catalin
