From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, Roland Dreier <rdreier@cisco.com>,
linux-kernel@vger.kernel.org, Nick Piggin <npiggin@suse.de>
Subject: Re: [S+Q2 07/19] slub: Allow removal of slab caches during boot
Date: Sat, 31 Jul 2010 12:41:14 +0300 [thread overview]
Message-ID: <4C53EFBA.4090900@cs.helsinki.fi> (raw)
In-Reply-To: <alpine.DEB.2.00.1007191058220.29361@router.home>
Christoph Lameter wrote:
>> Ok so I may be a bit sleepy or something but I still fail to see how
>> this whole thing isn't totally racy...
>>
>> AFAIK. By the time we switch the slab state, we -do- have all CPUs up
>> and can race happily between creating slab caches and creating the sysfs
>> files...
>
> If kmem_cache_init_late() is called after all other processors are up then
> we need to serialize the activities. But we cannot do that since the
> slub_lock is taken during kmalloc() for dynamic dma creation (lockdep
> will complain although we never use dma caches for sysfs....).
>
> After removal of dynamic dma creation we can take the lock for all of slab
> creation and removal.
>
> Like in the following patch:
>
> Subject: slub: Allow removal of slab caches during boot
>
> Serialize kmem_cache_create and kmem_cache_destroy using the slub_lock. Only
> possible after the use of the slub_lock during dynamic dma creation has been
> removed.
>
> Then make sure that the setup of the slab sysfs entries does not race
> with kmem_cache_create and kmem_cache destroy.
>
> If a slab cache is removed before we have setup sysfs then simply skip over
> the sysfs handling.
>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Roland Dreier <rdreier@cisco.com>
> Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Christoph, Ben, should I queue this up for 2.6.36?
>
> ---
> mm/slub.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c 2010-07-19 11:02:15.000000000 -0500
> +++ linux-2.6/mm/slub.c 2010-07-19 11:33:32.000000000 -0500
> @@ -2490,7 +2490,6 @@ void kmem_cache_destroy(struct kmem_cach
> s->refcount--;
> if (!s->refcount) {
> list_del(&s->list);
> - up_write(&slub_lock);
> if (kmem_cache_close(s)) {
> printk(KERN_ERR "SLUB %s: %s called for cache that "
> "still has objects.\n", s->name, __func__);
> @@ -2499,8 +2498,8 @@ void kmem_cache_destroy(struct kmem_cach
> if (s->flags & SLAB_DESTROY_BY_RCU)
> rcu_barrier();
> sysfs_slab_remove(s);
> - } else
> - up_write(&slub_lock);
> + }
> + up_write(&slub_lock);
> }
> EXPORT_SYMBOL(kmem_cache_destroy);
>
> @@ -3226,14 +3225,12 @@ struct kmem_cache *kmem_cache_create(con
> */
> s->objsize = max(s->objsize, (int)size);
> s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
> - up_write(&slub_lock);
>
> if (sysfs_slab_alias(s, name)) {
> - down_write(&slub_lock);
> s->refcount--;
> - up_write(&slub_lock);
> goto err;
> }
> + up_write(&slub_lock);
> return s;
> }
>
> @@ -3242,14 +3239,12 @@ struct kmem_cache *kmem_cache_create(con
> if (kmem_cache_open(s, GFP_KERNEL, name,
> size, align, flags, ctor)) {
> list_add(&s->list, &slab_caches);
> - up_write(&slub_lock);
> if (sysfs_slab_add(s)) {
> - down_write(&slub_lock);
> list_del(&s->list);
> - up_write(&slub_lock);
> kfree(s);
> goto err;
> }
> + up_write(&slub_lock);
> return s;
> }
> kfree(s);
> @@ -4507,6 +4502,13 @@ static int sysfs_slab_add(struct kmem_ca
>
> static void sysfs_slab_remove(struct kmem_cache *s)
> {
> + if (slab_state < SYSFS)
> + /*
> + * Sysfs has not been setup yet so no need to remove the
> + * cache from sysfs.
> + */
> + return;
> +
> kobject_uevent(&s->kobj, KOBJ_REMOVE);
> kobject_del(&s->kobj);
> kobject_put(&s->kobj);
> @@ -4552,8 +4554,11 @@ static int __init slab_sysfs_init(void)
> struct kmem_cache *s;
> int err;
>
> + down_write(&slub_lock);
> +
> slab_kset = kset_create_and_add("slab", &slab_uevent_ops, kernel_kobj);
> if (!slab_kset) {
> + up_write(&slub_lock);
> printk(KERN_ERR "Cannot register slab subsystem.\n");
> return -ENOSYS;
> }
> @@ -4578,6 +4583,7 @@ static int __init slab_sysfs_init(void)
> kfree(al);
> }
>
> + up_write(&slub_lock);
> resiliency_test();
> return 0;
> }
>
>
next prev parent reply other threads:[~2010-07-31 9:41 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-09 19:07 [S+Q2 00/19] SLUB with queueing (V2) beats SLAB netperf TCP_RR Christoph Lameter
2010-07-09 19:07 ` [S+Q2 01/19] Bugfix for semop() not reporting successful operation Christoph Lameter
2010-07-09 19:07 ` [S+Q2 02/19] percpu: make @dyn_size always mean min dyn_size in first chunk init functions Christoph Lameter
2010-07-09 19:07 ` [S+Q2 03/19] percpu: allow limited allocation before slab is online Christoph Lameter
2010-07-09 19:07 ` [S+Q2 04/19] slub: Use a constant for a unspecified node Christoph Lameter
2010-07-09 19:07 ` [S+Q2 05/19] SLUB: Constants need UL Christoph Lameter
2010-07-09 19:07 ` [S+Q2 06/19] slub: Check kasprintf results in kmem_cache_init() Christoph Lameter
2010-07-14 22:16 ` David Rientjes
2010-07-09 19:07 ` [S+Q2 07/19] slub: Allow removal of slab caches during boot Christoph Lameter
2010-07-14 23:48 ` David Rientjes
2010-07-19 0:07 ` Benjamin Herrenschmidt
2010-07-19 16:39 ` Christoph Lameter
2010-07-31 9:41 ` Pekka Enberg [this message]
2010-08-02 15:36 ` Christoph Lameter
2010-08-03 4:32 ` Pekka Enberg
2010-07-09 19:07 ` [S+Q2 08/19] slub: Use kmem_cache flags to detect if slab is in debugging mode Christoph Lameter
2010-07-09 19:07 ` [S+Q2 09/19] slub: discard_slab_unlock Christoph Lameter
2010-07-09 19:07 ` [S+Q2 10/19] slub: remove dynamic dma slab allocation Christoph Lameter
2010-07-09 19:07 ` [S+Q2 11/19] slub: Remove static kmem_cache_cpu array for boot Christoph Lameter
2010-07-09 19:07 ` [S+Q2 12/19] slub: Dynamically size kmalloc cache allocations Christoph Lameter
2010-07-09 19:07 ` [S+Q2 13/19] slub: Extract hooks for memory checkers from hotpaths Christoph Lameter
2010-07-09 19:07 ` [S+Q2 14/19] slub: Move gfpflag masking out of the hotpath Christoph Lameter
2010-07-09 19:07 ` [S+Q2 15/19] SLUB: Add SLAB style per cpu queueing Christoph Lameter
2010-07-09 19:07 ` [S+Q2 16/19] slub: Resize the new cpu queues Christoph Lameter
2010-07-09 19:07 ` [S+Q2 17/19] SLUB: Get rid of useless function count_free() Christoph Lameter
2010-07-09 19:07 ` [S+Q2 18/19] SLUB: Remove MAX_OBJS limitation Christoph Lameter
2010-07-09 19:07 ` [S+Q2 19/19] slub: Drop allocator announcement Christoph Lameter
2010-07-10 19:56 ` [S+Q2 00/19] SLUB with queueing (V2) beats SLAB netperf TCP_RR Heinz Diehl
2010-07-12 15:11 ` Christoph Lameter
2010-07-12 16:39 ` Heinz Diehl
2010-07-12 17:00 ` Christoph Lameter
2010-07-13 13:56 ` Heinz Diehl
2010-07-14 2:01 ` Christoph Lameter
2010-07-14 11:51 ` Tejun Heo
2010-07-14 14:25 ` Heinz Diehl
2010-07-14 20:22 ` David Rientjes
2010-07-14 11:46 ` Tejun Heo
2010-07-14 22:26 ` David Rientjes
2010-07-15 20:17 ` Christoph Lameter
2010-07-15 20:30 ` David Rientjes
2010-07-14 23:52 ` David Rientjes
2010-07-16 8:23 ` Pekka Enberg
2010-07-16 9:02 ` David Rientjes
2010-07-19 0:16 ` Benjamin Herrenschmidt
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