Messages in this thread | | | Date | Thu, 25 Feb 2010 16:31:00 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH] [4/4] SLAB: Fix node add timer race in cache_reap |
| |
On Thu, 25 Feb 2010, David Rientjes wrote:
> On Thu, 25 Feb 2010, Christoph Lameter wrote: > > > > I don't see how memory hotadd with a new node being onlined could have > > > worked fine before since slab lacked any memory hotplug notifier until > > > Andi just added it. > > > > AFAICR The cpu notifier took on that role in the past. > > > > The cpu notifier isn't involved if the firmware notifies the kernel that a > new ACPI memory device has been added or you write a start address to > /sys/devices/system/memory/probe. Hot-added memory devices can include > ACPI_SRAT_MEM_HOT_PLUGGABLE entries in the SRAT for x86 that assign them > non-online node ids (although all such entries get their bits set in > node_possible_map at boot), so a new pgdat may be allocated for the node's > registered range.
Yes Andi's work makes it explicit but there is already code in the cpu notifier (see cpuup_prepare) that seems to have been intended to initialize the node structures. Wonder why the hotplug people never addressed that issue? Kame?
list_for_each_entry(cachep, &cache_chain, next) { /* * Set up the size64 kmemlist for cpu before we can * begin anything. Make sure some other cpu on this * node has not already allocated this */ if (!cachep->nodelists[node]) { l3 = kmalloc_node(memsize, GFP_KERNEL, node); if (!l3) goto bad; kmem_list3_init(l3); l3->next_reap = jiffies + REAPTIMEOUT_LIST3 + ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
/* * The l3s don't come and go as CPUs come and * go. cache_chain_mutex is sufficient * protection here. */ cachep->nodelists[node] = l3; }
spin_lock_irq(&cachep->nodelists[node]->list_lock); cachep->nodelists[node]->free_limit = (1 + nr_cpus_node(node)) * cachep->batchcount + cachep->num; spin_unlock_irq(&cachep->nodelists[node]->list_lock); }
> kmalloc_node() in generic kernel code. All that is done under > MEM_GOING_ONLINE and not MEM_ONLINE, which is why I suggest the first and > fourth patch in this series may not be necessary if we prevent setting the > bit in the nodemask or building the zonelists until the slab nodelists are > ready.
That sounds good.
| |