lkml.org 
[lkml]   [2010]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [S+Q2 07/19] slub: Allow removal of slab caches during boot
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;
> }
>
>



\
 
 \ /
  Last update: 2010-07-31 11:43    [from the cache]
©2003-2011 Jasper Spaans