On 03/28/2016 08:26 AM, [email protected] wrote: > From: Joonsoo Kim <[email protected]> > > Major kmem_cache metadata in slab subsystem is synchronized with > the slab_mutex. In SLAB, if some of them is changed, node's shared > array cache would be freed and re-populated. If __kmem_cache_shrink() > is called at the same time, it will call drain_array() with n->shared > without holding node lock so problem can happen. > > We can fix this small theoretical race condition by holding node lock > in drain_array(), but, holding a slab_mutex in kmem_cache_shrink() > looks more appropriate solution because stable state would make things > less error-prone and this is not performance critical path. > > In addtion, annotate on SLAB functions.
Just a nit but would it not be better instead of doing comment-style annotation to use lockdep_assert_held/_once. In both cases for someone to understand what locks have to be held will go and read the source. In my mind it's easier to miss a comment line, rather than the lockdep_assert. Furthermore in case lockdep is enabled a locking violation would spew useful info to dmesg.
