The patch titled
slub: fix cpu hotplug offline/online path
has been added to the -mm tree. Its filename is
slub-place-kmem_cache_cpu-structures-in-a-numa-aware-way-fix.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: slub: fix cpu hotplug offline/online path
From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
On Wed, Oct 10, 2007 at 10:39:32AM -0700, Christoph Lameter wrote:
> On Wed, 10 Oct 2007, Akinobu Mita wrote:
>
> > I couldn't use get_cpu_slab() for that check. But I reviced the patch to do
> > what you said.
>
> Why would get_cpu_slab not work?
case CPU_DEAD:
case CPU_DEAD_FROZEN:
down_read(&slub_lock);
list_for_each_entry(s, &slab_caches, list) {
struct kmem_cache_cpu *c = get_cpu_slab(s, cpu);
local_irq_save(flags);
__flush_cpu_slab(s, cpu);
local_irq_restore(flags);
free_kmem_cache_cpu(c, cpu);
s->cpu_slab[cpu] = NULL; <----------------------
}
up_read(&slub_lock);
break;
When CPU is offlined, cpu-hotplug notifier sets s->cpu_slab[cpu] = NULL.
This means get_cpu_slab() always return NULL when CPU is being onlined.
So I can't use get_cpu_slab to check whether kmem_cache_cpu_free
initalization for the CPU has already been done or not.
>
> > + if (per_cpu(kmem_cache_cpu_free, cpu)) {
> > + /* Already initialized once */
> > + return;
> > + }
> > +
>
> kmem_cache_cpu_free is not only NULL if the cpu is not up yet but it is
> also NULL if the per cpu pool of kmem_cache_cpu structures was
> exhausted.
cpu-hotplug notifier by CPU_DEAD event frees kmem_cache_cpu structures
for the CPU being offlined. So we have 100 kmem_cache cpu structures
when the CPU will be onlined again.
But I agree that it is not so trivial. It is why I added the comment
/* Already initialized once */ in previous patch.
This is another approach for the fix.
Use cpumask to check whether kmem_cache_cpu_free initalization for
the CPU has already been done or not.
Acked-by: Christoph Lameter <clameter@xxxxxxx>
Cc: "Pekka Enberg" <penberg@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 6 ++++++
1 file changed, 6 insertions(+)
diff -puN mm/slub.c~slub-place-kmem_cache_cpu-structures-in-a-numa-aware-way-fix mm/slub.c
--- a/mm/slub.c~slub-place-kmem_cache_cpu-structures-in-a-numa-aware-way-fix
+++ a/mm/slub.c
@@ -1895,6 +1895,7 @@ static DEFINE_PER_CPU(struct kmem_cache_
kmem_cache_cpu)[NR_KMEM_CACHE_CPU];
static DEFINE_PER_CPU(struct kmem_cache_cpu *, kmem_cache_cpu_free);
+static cpumask_t kmem_cach_cpu_free_init_once = CPU_MASK_NONE;
static struct kmem_cache_cpu *alloc_kmem_cache_cpu(struct kmem_cache *s,
int cpu, gfp_t flags)
@@ -1969,8 +1970,13 @@ static void init_alloc_cpu_cpu(int cpu)
{
int i;
+ if (cpu_isset(cpu, kmem_cach_cpu_free_init_once))
+ return;
+
for (i = NR_KMEM_CACHE_CPU - 1; i >= 0; i--)
free_kmem_cache_cpu(&per_cpu(kmem_cache_cpu, cpu)[i], cpu);
+
+ cpu_set(cpu, kmem_cach_cpu_free_init_once);
}
static void __init init_alloc_cpu(void)
_
Patches currently in -mm which might be from akinobu.mita@xxxxxxxxx are
origin.patch
slub-place-kmem_cache_cpu-structures-in-a-numa-aware-way-fix.patch
module-return-error-when-mod_sysfs_init-failed.patch
cpu-hotplug-slab-cleanup-cpuup_callback.patch
cpu-hotplug-slab-fix-memory-leak-in-cpu-hotplug-error-path.patch
cpu-hotplug-cpu-deliver-cpu_up_canceled-only-to-notify_oked-callbacks-with-cpu_up_prepare.patch
cpu-hotplug-topology-remove-topology_dev_map.patch
cpu-hotplug-thermal_throttle-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-msr-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-mce-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling-fix-a-section-mismatch-warning.patch
do-cpu_dead-migrating-under-read_locktasklist-instead-of-write_lock_irqtasklist.patch
do-cpu_dead-migrating-under-read_locktasklist-instead-of-write_lock_irqtasklist-fix.patch
migration_callcpu_dead-use-spin_lock_irq-instead-of-task_rq_lock.patch
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