Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756173Ab0DWUys (ORCPT ); Fri, 23 Apr 2010 16:54:48 -0400 Received: from casper.infradead.org ([85.118.1.10]:59438 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753194Ab0DWUyp (ORCPT ); Fri, 23 Apr 2010 16:54:45 -0400 Subject: Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock From: Peter Zijlstra To: Greg Thelen Cc: KAMEZAWA Hiroyuki , Daisuke Nishimura , Vivek Goyal , balbir@linux.vnet.ibm.com, Andrea Righi , Trond Myklebust , Suleiman Souhlal , "Kirill A. Shutemov" , Andrew Morton , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org In-Reply-To: References: <1268609202-15581-2-git-send-email-arighi@develer.com> <20100318133527.420b2f25.kamezawa.hiroyu@jp.fujitsu.com> <20100318162855.GG18054@balbir.in.ibm.com> <20100319102332.f1d81c8d.kamezawa.hiroyu@jp.fujitsu.com> <20100319024039.GH18054@balbir.in.ibm.com> <20100319120049.3dbf8440.kamezawa.hiroyu@jp.fujitsu.com> <20100414140523.GC13535@redhat.com> <20100415114022.ef01b704.nishimura@mxp.nes.nec.co.jp> <20100415152104.62593f37.nishimura@mxp.nes.nec.co.jp> <20100415155432.cf1861d9.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 23 Apr 2010 22:54:34 +0200 Message-ID: <1272056074.1821.40.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1681 Lines: 52 On Fri, 2010-04-23 at 13:17 -0700, Greg Thelen wrote: > - lock_page_cgroup(pc); > + /* > + * Unless a page's cgroup reassignment is possible, then avoid grabbing > + * the lock used to protect the cgroup assignment. > + */ > + rcu_read_lock(); Where is the matching barrier? > + smp_rmb(); > + if (unlikely(mem_cgroup_account_move_ongoing)) { > + local_irq_save(flags); So the added irq-disable is a bug-fix? > + lock_page_cgroup(pc); > + locked = true; > + } > + > mem = pc->mem_cgroup; > if (!mem || !PageCgroupUsed(pc)) > goto done; > @@ -1449,6 +1468,7 @@ void mem_cgroup_update_file_mapped(struct page *page, int val) > /* > * Preemption is already disabled. We can use __this_cpu_xxx > */ > + VM_BUG_ON(preemptible()); Insta-bug here, there is nothing guaranteeing we're not preemptible here. > if (val > 0) { > __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]); > SetPageCgroupFileMapped(pc); > @@ -1458,7 +1478,11 @@ void mem_cgroup_update_file_mapped(struct page *page, int val) > } > > done: > - unlock_page_cgroup(pc); > + if (unlikely(locked)) { > + unlock_page_cgroup(pc); > + local_irq_restore(flags); > + } > + rcu_read_unlock(); > } -- 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/