On Wed, 2006-08-02 at 12:10 -0700, Ravikiran G Thirumalai wrote:
> Here's an attempt to educate lockdep about alien cache lock. tglx, can you
> confirm if this fixes the false positive? This is just an extension of the
> l3 lock lesson :).
>
> Note: With this approach, lockdep forgets its education for alien caches
> if all cpus of a node go down and come back up. But taking care of
> that scenario will make things uglier....not sure if it is worth it.
>
> Thanks,
> Kiran
Sorry, I did not come around to test it earlier. With this patch applied
the lockdep message is gone.
tglx
> Place the alien array cache locks of on slab malloc slab caches on a seperate
> lockdep class. This avoids false positives from lockdep
>
> Signed-off-by: Ravikiran Thirumalai <[email protected]>
> Signed-off-by: Shai Fultheim <[email protected]>
>
> Index: linux-2.6.18-rc3-x460/mm/slab.c
> ===================================================================
> --- linux-2.6.18-rc3-x460.orig/mm/slab.c 2006-07-30 21:27:28.000000000 -0700
> +++ linux-2.6.18-rc3-x460/mm/slab.c 2006-08-01 18:01:51.000000000 -0700
> @@ -682,23 +682,43 @@
> * The locking for this is tricky in that it nests within the locks
> * of all other slabs in a few places; to deal with this special
> * locking we put on-slab caches into a separate lock-class.
> + *
> + * We set lock class for alien array caches which are up during init.
> + * The lock annotation will be lost if all cpus of a node goes down and
> + * then comes back up during hotplug
> */
> -static struct lock_class_key on_slab_key;
> +static struct lock_class_key on_slab_l3_key;
> +static struct lock_class_key on_slab_alc_key;
> +
> +static inline void init_lock_keys(void)
>
> -static inline void init_lock_keys(struct cache_sizes *s)
> {
> int q;
> + struct cache_sizes *s = malloc_sizes;
>
> - for (q = 0; q < MAX_NUMNODES; q++) {
> - if (!s->cs_cachep->nodelists[q] || OFF_SLAB(s->cs_cachep))
> - continue;
> - lockdep_set_class(&s->cs_cachep->nodelists[q]->list_lock,
> - &on_slab_key);
> + while (s->cs_size != ULONG_MAX) {
> + for_each_node(q) {
> + struct array_cache **alc;
> + int r;
> + struct kmem_list3 *l3 = s->cs_cachep->nodelists[q];
> + if (!l3 || OFF_SLAB(s->cs_cachep))
> + continue;
> + lockdep_set_class(&l3->list_lock, &on_slab_l3_key);
> + alc = l3->alien;
> + if (!alc)
> + continue;
> + for_each_node(r) {
> + if (alc[r])
> + lockdep_set_class(&alc[r]->lock,
> + &on_slab_alc_key);
> + }
> + }
> + s++;
> }
> }
>
> #else
> -static inline void init_lock_keys(struct cache_sizes *s)
> +static inline void init_lock_keys()
> {
> }
> #endif
> @@ -1422,7 +1442,6 @@
> ARCH_KMALLOC_FLAGS|SLAB_PANIC,
> NULL, NULL);
> }
> - init_lock_keys(sizes);
>
> sizes->cs_dmacachep = kmem_cache_create(names->name_dma,
> sizes->cs_size,
> @@ -1495,6 +1514,10 @@
> mutex_unlock(&cache_chain_mutex);
> }
>
> + /* Annotate slab for lockdep -- annotate the malloc caches */
> + init_lock_keys();
> +
> +
> /* Done! */
> g_cpucache_up = FULL;
>
-
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