Hi Paul,
On Wed, 8 Mar 2017 11:46:33 +1100 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
>
> Today's linux-next merge of the rcu tree got a conflict in:
>
> mm/slab_common.c
>
> between commit:
>
> 657dc2f97220 ("slab: remove synchronous rcu_barrier() call in memcg cache release path")
>
> from Linus' tree and commit:
>
> 24b7cb25b8d1 ("mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU")
>
> from the rcu tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
That resolution was obviously wrong, the correct one is this:
diff --cc mm/slab_common.c
index 09d0e849b07f,296413c2bbcd..000000000000
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@@ -494,55 -458,29 +494,55 @@@ out_unlock
}
EXPORT_SYMBOL(kmem_cache_create);
-static int shutdown_cache(struct kmem_cache *s,
- struct list_head *release, bool *need_rcu_barrier)
+static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
{
- if (__kmem_cache_shutdown(s) != 0)
- return -EBUSY;
+ LIST_HEAD(to_destroy);
+ struct kmem_cache *s, *s2;
+
+ /*
- * On destruction, SLAB_DESTROY_BY_RCU kmem_caches are put on the
++ * On destruction, SLAB_TYPESAFE_BY_RCU kmem_caches are put on the
+ * @slab_caches_to_rcu_destroy list. The slab pages are freed
+ * through RCU and and the associated kmem_cache are dereferenced
+ * while freeing the pages, so the kmem_caches should be freed only
+ * after the pending RCU operations are finished. As rcu_barrier()
+ * is a pretty slow operation, we batch all pending destructions
+ * asynchronously.
+ */
+ mutex_lock(&slab_mutex);
+ list_splice_init(&slab_caches_to_rcu_destroy, &to_destroy);
+ mutex_unlock(&slab_mutex);
+
+ if (list_empty(&to_destroy))
+ return;
- if (s->flags & SLAB_TYPESAFE_BY_RCU)
- *need_rcu_barrier = true;
+ rcu_barrier();
- list_move(&s->list, release);
- return 0;
+ list_for_each_entry_safe(s, s2, &to_destroy, list) {
+#ifdef SLAB_SUPPORTS_SYSFS
+ sysfs_slab_release(s);
+#else
+ slab_kmem_cache_release(s);
+#endif
+ }
}
-static void release_caches(struct list_head *release, bool need_rcu_barrier)
+static int shutdown_cache(struct kmem_cache *s)
{
- struct kmem_cache *s, *s2;
+ /* free asan quarantined objects */
+ kasan_cache_shutdown(s);
- if (need_rcu_barrier)
- rcu_barrier();
+ if (__kmem_cache_shutdown(s) != 0)
+ return -EBUSY;
- list_for_each_entry_safe(s, s2, release, list) {
+ memcg_unlink_cache(s);
+ list_del(&s->list);
+
- if (s->flags & SLAB_DESTROY_BY_RCU) {
++ if (s->flags & SLAB_TYPESAFE_BY_RCU) {
+ list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
+ schedule_work(&slab_caches_to_rcu_destroy_work);
+ } else {
#ifdef SLAB_SUPPORTS_SYSFS
- sysfs_slab_remove(s);
+ sysfs_slab_release(s);
#else
slab_kmem_cache_release(s);
#endif
--
Cheers,
Stephen Rothwell
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