From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fgwmail9.fujitsu.co.jp (fgwmail9.fujitsu.co.jp [192.51.44.39]) by ozlabs.org (Postfix) with ESMTP id D81C2B7D6D for ; Mon, 15 Mar 2010 12:31:17 +1100 (EST) Received: from fgwmail5.fujitsu.co.jp (fgwmail5.fujitsu.co.jp [192.51.44.35]) by fgwmail9.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2F15iBV015300 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 15 Mar 2010 10:05:44 +0900 Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2F15gbD015938 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 15 Mar 2010 10:05:42 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 7855C45DE4F for ; Mon, 15 Mar 2010 10:05:42 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 4DC0F45DE4E for ; Mon, 15 Mar 2010 10:05:42 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 37EAA1DB8040 for ; Mon, 15 Mar 2010 10:05:42 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id DAE7D1DB803F for ; Mon, 15 Mar 2010 10:05:38 +0900 (JST) Date: Mon, 15 Mar 2010 10:02:02 +0900 From: KAMEZAWA Hiroyuki To: Sachin Sant Subject: [BUGFIX][PATCH] memcg: avoid use cmpxchg in swap cgroup maintainance (Was Re: 34-rc1-git3 build failure with CGROUP_MEM_RES_CTLR_SWAP=y Message-Id: <20100315100202.eb735f59.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <4B9CBEE6.1090509@in.ibm.com> References: <4B9CBEE6.1090509@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: nishimura@mxp.nes.nec.co.jp, lizf@cn.fujitsu.com, linux-kernel , Linux/PPC Development , "akpm@linux-foundation.org" , Balbir Singh List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, 14 Mar 2010 16:18:06 +0530 Sachin Sant wrote: > On a PowerPC box, latest 34-rc1 git(d89b218b8...) fails to build > with CGROUPS_MEM_RES_CTRL_SWAP=y. > > LD init/built-in.o > LD .tmp_vmlinux1 > mm/built-in.o: In function __xchg: > arch/powerpc/include/asm/system.h:331: undefined reference to .__xchg_called_with_bad_pointer > mm/built-in.o: In function __cmpxchg: > arch/powerpc/include/asm/system.h:474: undefined reference to .__cmpxchg_called_with_bad_pointer > make: *** [.tmp_vmlinux1] Error 1 > > The code in question was added via commit 024914477e... > > memcg: move charges of anonymous swap > Oh..ok, powerpc (and other archs?) can't do 2byte cmpxchg and xchg. Then, we should use spinlock rather than that. How about this ? Nishimura-san, could you consider something better ? We need a quick fix. == swap_cgroup uses 2bytes data and uses cmpxchg in a new operation. 2byte cmpxchg/xchg is not available on some archs. This patch replaces cmpxchg/xchg with operations under lock. Signed-off-by: KAMEZAWA Hiroyuki --- mm/page_cgroup.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) Index: mmotm-2.6.34-Mar11/mm/page_cgroup.c =================================================================== --- mmotm-2.6.34-Mar11.orig/mm/page_cgroup.c +++ mmotm-2.6.34-Mar11/mm/page_cgroup.c @@ -284,6 +284,7 @@ static DEFINE_MUTEX(swap_cgroup_mutex); struct swap_cgroup_ctrl { struct page **map; unsigned long length; + spinlock_t lock; }; struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES]; @@ -353,16 +354,22 @@ unsigned short swap_cgroup_cmpxchg(swp_e struct swap_cgroup_ctrl *ctrl; struct page *mappage; struct swap_cgroup *sc; + unsigned long flags; + unsigned short retval; ctrl = &swap_cgroup_ctrl[type]; mappage = ctrl->map[idx]; sc = page_address(mappage); sc += pos; - if (cmpxchg(&sc->id, old, new) == old) - return old; + spin_lock_irqsave(&ctrl->lock, flags); + retval = sc->id; + if (retval == old) + sc->id = new; else - return 0; + retval = 0; + spin_unlock_irqrestore(&ctrl->lock, flags); + return retval; } /** @@ -383,13 +390,17 @@ unsigned short swap_cgroup_record(swp_en struct page *mappage; struct swap_cgroup *sc; unsigned short old; + unsigned long flags; ctrl = &swap_cgroup_ctrl[type]; mappage = ctrl->map[idx]; sc = page_address(mappage); sc += pos; - old = xchg(&sc->id, id); + spin_lock_irqsave(&ctrl->lock, flags); + old = sc->id; + sc->id = id; + spin_unlock_irqrestore(&ctrl->lock, flags); return old; } @@ -441,6 +452,7 @@ int swap_cgroup_swapon(int type, unsigne mutex_lock(&swap_cgroup_mutex); ctrl->length = length; ctrl->map = array; + spin_lock_init(&ctrl->lock); if (swap_cgroup_prepare(type)) { /* memory shortage */ ctrl->map = NULL;