From 4eaf3f64397c3db3c5785eee508270d62a9fabd9 Mon Sep 17 00:00:00 2001 From: Haicheng Li Date: Mon, 24 May 2010 14:32:52 -0700 Subject: mem-hotplug: fix potential race while building zonelist for new populated zone Add global mutex zonelists_mutex to fix the possible race: CPU0 CPU1 CPU2 (1) zone->present_pages += online_pages; (2) build_all_zonelists(); (3) alloc_page(); (4) free_page(); (5) build_all_zonelists(); (6) __build_all_zonelists(); (7) zone->pageset = alloc_percpu(); In step (3,4), zone->pageset still points to boot_pageset, so bad things may happen if 2+ nodes are in this state. Even if only 1 node is accessing the boot_pageset, (3) may still consume too much memory to fail the memory allocations in step (7). Besides, atomic operation ensures alloc_percpu() in step (7) will never fail since there is a new fresh memory block added in step(6). [haicheng.li@linux.intel.com: hold zonelists_mutex when build_all_zonelists] Signed-off-by: Haicheng Li Signed-off-by: Wu Fengguang Reviewed-by: Andi Kleen Cc: Christoph Lameter Cc: Mel Gorman Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cpu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/cpu.c b/kernel/cpu.c index 3e8b3ba27175..124ad9d6be16 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -357,8 +357,11 @@ int __cpuinit cpu_up(unsigned int cpu) return -ENOMEM; } - if (pgdat->node_zonelists->_zonerefs->zone == NULL) + if (pgdat->node_zonelists->_zonerefs->zone == NULL) { + mutex_lock(&zonelists_mutex); build_all_zonelists(NULL); + mutex_unlock(&zonelists_mutex); + } #endif cpu_maps_update_begin(); -- cgit v1.2.3