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Date: Mon, 23 Nov 2009 22:01:15 +0200
From: Pekka Enberg <penberg@...helsinki.fi>
To: Christoph Lameter <cl@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>, paulmck@...ux.vnet.ibm.com,
linux-mm@...ck.org, mpm@...enic.com,
LKML <linux-kernel@...r.kernel.org>,
Nick Piggin <npiggin@...e.de>
Subject: Re: lockdep complaints in slab allocator
On Mon, 2009-11-23 at 21:50 +0200, Pekka Enberg wrote:
> On Mon, 23 Nov 2009, Pekka Enberg wrote:
> > > That turns out to be _very_ hard. How about something like the following
> > > untested patch which delays slab_destroy() while we're under nc->lock.
>
> On Mon, 2009-11-23 at 13:30 -0600, Christoph Lameter wrote:
> > Code changes to deal with a diagnostic issue?
>
> OK, fair enough. If I suffer permanent brain damage from staring at the
> SLAB code for too long, I hope you and Matt will chip in to pay for my
> medication.
>
> I think I was looking at the wrong thing here. The problem is in
> cache_free_alien() so the comment in slab_destroy() isn't relevant.
> Looking at init_lock_keys() we already do special lockdep annotations
> but there's a catch (as explained in a comment on top of
> on_slab_alc_key):
>
> * 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
>
> Paul said he was running CPU hotplug so maybe that explains the problem?
Maybe something like this untested patch fixes the issue...
Pekka
diff --git a/mm/slab.c b/mm/slab.c
index 7dfa481..84de47e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -604,6 +604,26 @@ static struct kmem_cache cache_cache = {
#define BAD_ALIEN_MAGIC 0x01020304ul
+/*
+ * chicken and egg problem: delay the per-cpu array allocation
+ * until the general caches are up.
+ */
+static enum {
+ NONE,
+ PARTIAL_AC,
+ PARTIAL_L3,
+ EARLY,
+ FULL
+} g_cpucache_up;
+
+/*
+ * used by boot code to determine if it can use slab based allocator
+ */
+int slab_is_available(void)
+{
+ return g_cpucache_up >= EARLY;
+}
+
#ifdef CONFIG_LOCKDEP
/*
@@ -620,40 +640,52 @@ static struct kmem_cache cache_cache = {
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 void init_node_lock_keys(int q)
{
- int q;
struct cache_sizes *s = malloc_sizes;
- 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;
- /*
- * FIXME: This check for BAD_ALIEN_MAGIC
- * should go away when common slab code is taught to
- * work even without alien caches.
- * Currently, non NUMA code returns BAD_ALIEN_MAGIC
- * for alloc_alien_cache,
- */
- if (!alc || (unsigned long)alc == BAD_ALIEN_MAGIC)
- continue;
- for_each_node(r) {
- if (alc[r])
- lockdep_set_class(&alc[r]->lock,
- &on_slab_alc_key);
- }
+ if (g_cpucache_up != FULL)
+ return;
+
+ for (s = malloc_sizes; s->cs_size != ULONG_MAX; s++) {
+ struct array_cache **alc;
+ struct kmem_list3 *l3;
+ int r;
+
+ l3 = s->cs_cachep->nodelists[q];
+ if (!l3 || OFF_SLAB(s->cs_cachep))
+ return;
+ lockdep_set_class(&l3->list_lock, &on_slab_l3_key);
+ alc = l3->alien;
+ /*
+ * FIXME: This check for BAD_ALIEN_MAGIC
+ * should go away when common slab code is taught to
+ * work even without alien caches.
+ * Currently, non NUMA code returns BAD_ALIEN_MAGIC
+ * for alloc_alien_cache,
+ */
+ if (!alc || (unsigned long)alc == BAD_ALIEN_MAGIC)
+ return;
+ for_each_node(r) {
+ if (alc[r])
+ lockdep_set_class(&alc[r]->lock,
+ &on_slab_alc_key);
}
- s++;
}
}
+
+static inline void init_lock_keys(void)
+{
+ int node;
+
+ for_each_node(node)
+ init_node_lock_keys(node);
+}
#else
+static void init_node_lock_keys(int q)
+{
+}
+
static inline void init_lock_keys(void)
{
}
@@ -665,26 +697,6 @@ static inline void init_lock_keys(void)
static DEFINE_MUTEX(cache_chain_mutex);
static struct list_head cache_chain;
-/*
- * chicken and egg problem: delay the per-cpu array allocation
- * until the general caches are up.
- */
-static enum {
- NONE,
- PARTIAL_AC,
- PARTIAL_L3,
- EARLY,
- FULL
-} g_cpucache_up;
-
-/*
- * used by boot code to determine if it can use slab based allocator
- */
-int slab_is_available(void)
-{
- return g_cpucache_up >= EARLY;
-}
-
static DEFINE_PER_CPU(struct delayed_work, reap_work);
static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
@@ -1254,6 +1266,8 @@ static int __cpuinit cpuup_prepare(long cpu)
kfree(shared);
free_alien_cache(alien);
}
+ init_node_lock_keys(node);
+
return 0;
bad:
cpuup_canceled(cpu);
--
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