slab: add __kmem_cache_destroy()

Like __kmem_cache_create(), it operates on a KC whose memory is managed
by the caller.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>

kern/include/slab.h

diff --git a/kern/include/slab.h b/kern/include/slab.h
index 509b823..f014f83 100644
--- a/kern/include/slab.h
+++ b/kern/include/slab.h
@@ -162,12 +162,13 @@
 void kmem_cache_init(void);
 void kmem_cache_reap(struct kmem_cache *cp);
 unsigned int kmc_nr_pcpu_caches(void);
-/* Low-level interface for initializing a cache. */
+/* Low-level interface for creating/destroying; caller manages kc's memory */
 void __kmem_cache_create(struct kmem_cache *kc, const char *name,
                          size_t obj_size, int align, int flags,
                          struct arena *source,
                          int (*ctor)(void *, void *, int),
                          void (*dtor)(void *, void *), void *priv);
+void __kmem_cache_destroy(struct kmem_cache *cp);
 
 /* Tracing */
 int kmem_trace_start(struct kmem_cache *kc);

kern/src/slab.c

diff --git a/kern/src/slab.c b/kern/src/slab.c
index 995ba31..0ebc730 100644
--- a/kern/src/slab.c
+++ b/kern/src/slab.c
@@ -490,7 +490,7 @@
 
 /* Once you call destroy, never use this cache again... o/w there may be weird
  * races, and other serious issues.  */
-void kmem_cache_destroy(struct kmem_cache *cp)
+void __kmem_cache_destroy(struct kmem_cache *cp)
 {
 	struct kmem_slab *a_slab, *next;
 
@@ -520,6 +520,11 @@
 	}
 	spin_unlock_irqsave(&cp->cache_lock);
 	kmem_trace_warn_notempty(cp);
+}
+
+void kmem_cache_destroy(struct kmem_cache *cp)
+{
+	__kmem_cache_destroy(cp);
 	kmem_cache_free(kmem_cache_cache, cp);
 }