From 925268a06dc2b1ff7bfcc37419a6827a0e739639 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Tue, 11 Jan 2011 16:44:01 +0900 Subject: memory hotplug: one more lock on memory hotplug Now, memory_hotplug_(un)lock() is used for add/remove/offline pages for avoiding races with hibernation. But this should be held in online_pages(), too. It seems asymmetric. There are cases where one has to avoid a race with memory hotplug notifier and his own local code, and hotplug v.s. hotplug. This will add a generic solution for avoiding races. In other view, having lock here has no big impacts. online pages is tend to be done by udev script at el against each memory section one by one. Then, it's better to have lock here, too. Cc: # 2.6.37 Reviewed-by: Christoph Lameter Acked-by: David Rientjes Signed-off-by: KAMEZAWA Hiroyuki Signed-off-by: Pekka Enberg --- mm/memory_hotplug.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'mm') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 2c6523af5473..83163c096a75 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -407,6 +407,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) int ret; struct memory_notify arg; + lock_memory_hotplug(); arg.start_pfn = pfn; arg.nr_pages = nr_pages; arg.status_change_nid = -1; @@ -419,6 +420,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) ret = notifier_to_errno(ret); if (ret) { memory_notify(MEM_CANCEL_ONLINE, &arg); + unlock_memory_hotplug(); return ret; } /* @@ -443,6 +445,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) printk(KERN_DEBUG "online_pages %lx at %lx failed\n", nr_pages, pfn); memory_notify(MEM_CANCEL_ONLINE, &arg); + unlock_memory_hotplug(); return ret; } @@ -467,6 +470,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages) if (onlined_pages) memory_notify(MEM_ONLINE, &arg); + unlock_memory_hotplug(); return 0; } -- cgit v1.2.3-58-ga151 From 04d94879c8a4973b5499dc26b9d38acee8928791 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Mon, 10 Jan 2011 10:15:15 -0600 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() currently does not acquire the memory_hotplug lock. Another patch will be submitted by the memory hotplug authors to take the memory hotplug lock and describe the uses of the memory hotplug lock to protect against adding and removal of nodes from non hotplug data structures. Cc: # 2.6.37 Reported-and-tested-by: Bart Van Assche Acked-by: David Rientjes Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg --- mm/slub.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm') diff --git a/mm/slub.c b/mm/slub.c index bec0e355fbad..96e690717822 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3821,7 +3821,7 @@ static ssize_t show_slab_objects(struct kmem_cache *s, } } - 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 kmem_cache *s, 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"); } -- cgit v1.2.3-58-ga151