Messages in this thread | | | Date | Fri, 1 Apr 2016 11:18:07 +0900 | From | Joonsoo Kim <> | Subject | Re: [PATCH 01/11] mm/slab: hold a slab_mutex when calling __kmem_cache_shrink() |
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On Thu, Mar 31, 2016 at 01:53:14PM +0300, Nikolay Borisov wrote: > > > On 03/28/2016 08:26 AM, js1304@gmail.com wrote: > > From: Joonsoo Kim <iamjoonsoo.kim@lge.com> > > > > 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.
Good idea. I'm not sure if lockdep_assert is best fit but I will add something to check it rather than just adding the comment.
Thanks.
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