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Commit ce79ddc8 authored by Pekka Enberg's avatar Pekka Enberg
Browse files

SLAB: Fix lockdep annotations for CPU hotplug 



As reported by Paul McKenney:

  I am seeing some lockdep complaints in rcutorture runs that include
  frequent CPU-hotplug operations.  The tests are otherwise successful.
  My first thought was to send a patch that gave each array_cache
  structure's ->lock field its own struct lock_class_key, but you already
  have a init_lock_keys() that seems to be intended to deal with this.

  ------------------------------------------------------------------------

  =============================================
  [ INFO: possible recursive locking detected ]
  2.6.32-rc4-autokern1 #1
  ---------------------------------------------
  syslogd/2908 is trying to acquire lock:
   (&nc->lock){..-...}, at: [<c0000000001407f4>] .kmem_cache_free+0x118/0x2d4

  but task is already holding lock:
   (&nc->lock){..-...}, at: [<c0000000001411bc>] .kfree+0x1f0/0x324

  other info that might help us debug this:
  3 locks held by syslogd/2908:
   #0:  (&u->readlock){+.+.+.}, at: [<c0000000004556f8>] .unix_dgram_recvmsg+0x70/0x338
   #1:  (&nc->lock){..-...}, at: [<c0000000001411bc>] .kfree+0x1f0/0x324
   #2:  (&parent->list_lock){-.-...}, at: [<c000000000140f64>] .__drain_alien_cache+0x50/0xb8

  stack backtrace:
  Call Trace:
  [c0000000e8ccafc0] [c0000000000101e4] .show_stack+0x70/0x184 (unreliable)
  [c0000000e8ccb070] [c0000000000afebc] .validate_chain+0x6ec/0xf58
  [c0000000e8ccb180] [c0000000000b0ff0] .__lock_acquire+0x8c8/0x974
  [c0000000e8ccb280] [c0000000000b2290] .lock_acquire+0x140/0x18c
  [c0000000e8ccb350] [c000000000468df0] ._spin_lock+0x48/0x70
  [c0000000e8ccb3e0] [c0000000001407f4] .kmem_cache_free+0x118/0x2d4
  [c0000000e8ccb4a0] [c000000000140b90] .free_block+0x130/0x1a8
  [c0000000e8ccb540] [c000000000140f94] .__drain_alien_cache+0x80/0xb8
  [c0000000e8ccb5e0] [c0000000001411e0] .kfree+0x214/0x324
  [c0000000e8ccb6a0] [c0000000003ca860] .skb_release_data+0xe8/0x104
  [c0000000e8ccb730] [c0000000003ca2ec] .__kfree_skb+0x20/0xd4
  [c0000000e8ccb7b0] [c0000000003cf2c8] .skb_free_datagram+0x1c/0x5c
  [c0000000e8ccb830] [c00000000045597c] .unix_dgram_recvmsg+0x2f4/0x338
  [c0000000e8ccb920] [c0000000003c0f14] .sock_recvmsg+0xf4/0x13c
  [c0000000e8ccbb30] [c0000000003c28ec] .SyS_recvfrom+0xb4/0x130
  [c0000000e8ccbcb0] [c0000000003bfb78] .sys_recv+0x18/0x2c
  [c0000000e8ccbd20] [c0000000003ed388] .compat_sys_recv+0x14/0x28
  [c0000000e8ccbd90] [c0000000003ee1bc] .compat_sys_socketcall+0x178/0x220
  [c0000000e8ccbe30] [c0000000000085d4] syscall_exit+0x0/0x40

This patch fixes the issue by setting up lockdep annotations during CPU
hotplug.

Reported-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
parent 648f4e3e

mm/slab.c

+61 −47
Original line number Original line Diff line number Diff line
@@ -604,6 +604,26 @@ static struct kmem_cache cache_cache = { 




#define BAD_ALIEN_MAGIC 0x01020304ul

#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

#ifdef CONFIG_LOCKDEP





/*

/*
@@ -620,19 +640,21 @@ static struct kmem_cache cache_cache = { 
static struct lock_class_key on_slab_l3_key;

static struct lock_class_key on_slab_l3_key;

static struct lock_class_key on_slab_alc_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;

	struct cache_sizes *s = malloc_sizes;





	while (s->cs_size != ULONG_MAX) {

	if (g_cpucache_up != FULL)

		for_each_node(q) {

		return;



	for (s = malloc_sizes; s->cs_size != ULONG_MAX; s++) {

		struct array_cache **alc;

		struct array_cache **alc;

		struct kmem_list3 *l3;

		int r;

		int r;

			struct kmem_list3 *l3 = s->cs_cachep->nodelists[q];



		l3 = s->cs_cachep->nodelists[q];

		if (!l3 || OFF_SLAB(s->cs_cachep))

		if (!l3 || OFF_SLAB(s->cs_cachep))

				continue;

			return;

		lockdep_set_class(&l3->list_lock, &on_slab_l3_key);

		lockdep_set_class(&l3->list_lock, &on_slab_l3_key);

		alc = l3->alien;

		alc = l3->alien;

		/*

		/*
@@ -643,17 +665,27 @@ static inline void init_lock_keys(void) 
		 * for alloc_alien_cache,

		 * for alloc_alien_cache,

		 */

		 */

		if (!alc || (unsigned long)alc == BAD_ALIEN_MAGIC)

		if (!alc || (unsigned long)alc == BAD_ALIEN_MAGIC)

				continue;

			return;

		for_each_node(r) {

		for_each_node(r) {

			if (alc[r])

			if (alc[r])

				lockdep_set_class(&alc[r]->lock,

				lockdep_set_class(&alc[r]->lock,

					&on_slab_alc_key);

					&on_slab_alc_key);

		}

		}

	}

	}

		s++;

}

}



static inline void init_lock_keys(void)

{

	int node;



	for_each_node(node)

		init_node_lock_keys(node);

}

}

#else

#else

static void init_node_lock_keys(int q)

{

}



static inline void init_lock_keys(void)

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 DEFINE_MUTEX(cache_chain_mutex);

static struct list_head cache_chain;

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 DEFINE_PER_CPU(struct delayed_work, reap_work);





static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)

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);

		kfree(shared);

		free_alien_cache(alien);

		free_alien_cache(alien);

	}

	}

	init_node_lock_keys(node);



	return 0;

	return 0;

bad:

bad:

	cpuup_canceled(cpu);

	cpuup_canceled(cpu);