Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754415Ab3HLTgE (ORCPT ); Mon, 12 Aug 2013 15:36:04 -0400 Received: from g1t0028.austin.hp.com ([15.216.28.35]:14226 "EHLO g1t0028.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751915Ab3HLTgB (ORCPT ); Mon, 12 Aug 2013 15:36:01 -0400 From: Toshi Kani To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, rjw@sisk.pl, kosaki.motohiro@jp.fujitsu.com, kamezawa.hiroyu@jp.fujitsu.com, tangchen@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, liwanp@linux.vnet.ibm.com, Toshi Kani Subject: [PATCH] mm/hotplug: Remove stop_machine() from try_offline_node() Date: Mon, 12 Aug 2013 13:34:31 -0600 Message-Id: <1376336071-9128-1-git-send-email-toshi.kani@hp.com> X-Mailer: git-send-email 1.8.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3482 Lines: 115 lock_device_hotplug() serializes hotplug & online/offline operations. The lock is held in common sysfs online/offline interfaces and ACPI hotplug code paths. try_offline_node() off-lines a node if all memory sections and cpus are removed on the node. It is called from acpi_processor_remove() and acpi_memory_remove_memory()->remove_memory() paths, both of which are in the ACPI hotplug code. try_offline_node() calls stop_machine() to stop all cpus while checking all cpu status with the assumption that the caller is not protected from CPU hotplug or CPU online/offline operations. However, the caller is always serialized with lock_device_hotplug(). Also, the code needs to be properly serialized with a lock, not by stopping all cpus at a random place with stop_machine(). This patch removes the use of stop_machine() in try_offline_node() and adds comments to try_offline_node() and remove_memory() that lock_device_hotplug() is required. Signed-off-by: Toshi Kani --- mm/memory_hotplug.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index ca1dd3a..0b4b0f7 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1674,9 +1674,8 @@ static int is_memblock_offlined_cb(struct memory_block *mem, void *arg) return ret; } -static int check_cpu_on_node(void *data) +static int check_cpu_on_node(pg_data_t *pgdat) { - struct pglist_data *pgdat = data; int cpu; for_each_present_cpu(cpu) { @@ -1691,10 +1690,9 @@ static int check_cpu_on_node(void *data) return 0; } -static void unmap_cpu_on_node(void *data) +static void unmap_cpu_on_node(pg_data_t *pgdat) { #ifdef CONFIG_ACPI_NUMA - struct pglist_data *pgdat = data; int cpu; for_each_possible_cpu(cpu) @@ -1703,10 +1701,11 @@ static void unmap_cpu_on_node(void *data) #endif } -static int check_and_unmap_cpu_on_node(void *data) +static int check_and_unmap_cpu_on_node(pg_data_t *pgdat) { - int ret = check_cpu_on_node(data); + int ret; + ret = check_cpu_on_node(pgdat); if (ret) return ret; @@ -1715,11 +1714,18 @@ static int check_and_unmap_cpu_on_node(void *data) * the cpu_to_node() now. */ - unmap_cpu_on_node(data); + unmap_cpu_on_node(pgdat); return 0; } -/* offline the node if all memory sections of this node are removed */ +/** + * try_offline_node + * + * Offline a node if all memory sections and cpus of the node are removed. + * + * NOTE: The caller must call lock_device_hotplug() to serialize hotplug + * and online/offline operations before this call. + */ void try_offline_node(int nid) { pg_data_t *pgdat = NODE_DATA(nid); @@ -1745,7 +1751,7 @@ void try_offline_node(int nid) return; } - if (stop_machine(check_and_unmap_cpu_on_node, pgdat, NULL)) + if (check_and_unmap_cpu_on_node(pgdat)) return; /* @@ -1782,6 +1788,13 @@ void try_offline_node(int nid) } EXPORT_SYMBOL(try_offline_node); +/** + * remove_memory + * + * NOTE: The caller must call lock_device_hotplug() to serialize hotplug + * and online/offline operations before this call, as required by + * try_offline_node(). + */ void __ref remove_memory(int nid, u64 start, u64 size) { int ret; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/