Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755581Ab0GaJld (ORCPT ); Sat, 31 Jul 2010 05:41:33 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:41290 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755340Ab0GaJlb (ORCPT ); Sat, 31 Jul 2010 05:41:31 -0400 Message-ID: <4C53EFBA.4090900@cs.helsinki.fi> Date: Sat, 31 Jul 2010 12:41:14 +0300 From: Pekka Enberg User-Agent: Thunderbird 2.0.0.24 (Macintosh/20100228) MIME-Version: 1.0 To: Christoph Lameter CC: Benjamin Herrenschmidt , David Rientjes , linux-mm@kvack.org, Roland Dreier , linux-kernel@vger.kernel.org, Nick Piggin Subject: Re: [S+Q2 07/19] slub: Allow removal of slab caches during boot References: <20100709190706.938177313@quilx.com> <20100709190853.770833931@quilx.com> <1279498030.10390.1760.camel@pasglop> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4299 Lines: 138 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 > Cc: Roland Dreier > Signed-off-by: Christoph Lameter 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; > } > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/