Messages in this thread Patch in this message | | | Date | Fri, 7 Jan 2011 09:22:46 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH] slub: Fix sysfs circular locking dependency |
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On Fri, 7 Jan 2011, KAMEZAWA Hiroyuki wrote:
> But, nice catch. I think MEM_GOING_ONLINE, MEM_ONLINE should be done under > lock_memory_hotplug. So, could you update your patch and modify online_pages() ? > > IIUC, online_pages() is an user interface function and there will be no downside > to insert lock there. online_pages() should be serialized.
Subject: slub: Avoid use of slub_lock in show_slab_objects()
The purpose of the locking is to prevent removal and additions of nodes when statistics are gathered for a slab cache. So we need to avoid racing with memory hotplug functionality.
It is enough to take the memory hotplug locks there instead of the slub_lock.
online_pages() does not acquire the memory_hotplug lock. So add the missing locking there.
Signed-off-by: Christoph Lameter <cl@linux.com>
--- mm/memory_hotplug.c | 17 +++++++++++------ mm/slub.c | 4 ++-- 2 files changed, 13 insertions(+), 8 deletions(-)
Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2011-01-07 09:17:35.000000000 -0600 +++ linux-2.6/mm/slub.c 2011-01-07 09:17:38.000000000 -0600 @@ -3821,7 +3821,7 @@ static ssize_t show_slab_objects(struct } }
- down_read(&slub_lock); + lock_memory_hotplug(); #ifdef CONFIG_SLUB_DEBUG if (flags & SO_ALL) { for_each_node_state(node, N_NORMAL_MEMORY) { @@ -3862,7 +3862,7 @@ static ssize_t show_slab_objects(struct x += sprintf(buf + x, " N%d=%lu", node, nodes[node]); #endif - up_read(&slub_lock); + unlock_memory_hotplug(); kfree(nodes); return x + sprintf(buf + x, "\n"); } Index: linux-2.6/mm/memory_hotplug.c =================================================================== --- linux-2.6.orig/mm/memory_hotplug.c 2011-01-07 09:17:59.000000000 -0600 +++ linux-2.6/mm/memory_hotplug.c 2011-01-07 09:20:07.000000000 -0600 @@ -415,12 +415,12 @@ int online_pages(unsigned long pfn, unsi if (node_present_pages(nid) == 0) arg.status_change_nid = nid;
+ lock_memory_hotplug(); ret = memory_notify(MEM_GOING_ONLINE, &arg); ret = notifier_to_errno(ret); - if (ret) { - memory_notify(MEM_CANCEL_ONLINE, &arg); - return ret; - } + if (ret) + goto cancel; + /* * This doesn't need a lock to do pfn_to_page(). * The section can't be removed here because of the @@ -442,8 +442,7 @@ int online_pages(unsigned long pfn, unsi mutex_unlock(&zonelists_mutex); printk(KERN_DEBUG "online_pages %lx at %lx failed\n", nr_pages, pfn); - memory_notify(MEM_CANCEL_ONLINE, &arg); - return ret; + goto cancel; }
zone->present_pages += onlined_pages; @@ -468,7 +467,13 @@ int online_pages(unsigned long pfn, unsi if (onlined_pages) memory_notify(MEM_ONLINE, &arg);
+ unlock_memory_hotplug(); return 0; + +cancel: + memory_notify(MEM_CANCEL_ONLINE, &arg); + unlock_memory_hotplug(); + return ret; } #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
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