From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755496Ab1KIRCz (ORCPT ); Wed, 9 Nov 2011 12:02:55 -0500 Received: from mail-pz0-f42.google.com ([209.85.210.42]:52516 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751285Ab1KIRCy (ORCPT ); Wed, 9 Nov 2011 12:02:54 -0500 Date: Wed, 9 Nov 2011 09:02:48 -0800 From: Tejun Heo To: Andrea Arcangeli , Oleg Nesterov Cc: "Srivatsa S. Bhat" , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Jiri Slaby , linux-mm@kvack.org, Andrew Morton Subject: Re: [PATCH] thp: reduce khugepaged freezing latency Message-ID: <20111109170248.GD1260@google.com> References: <4EB8E969.6010502@suse.cz> <1320766151-2619-1-git-send-email-aarcange@redhat.com> <1320766151-2619-2-git-send-email-aarcange@redhat.com> <4EB98A83.3040101@linux.vnet.ibm.com> <4EBA75F2.4080800@linux.vnet.ibm.com> <20111109155342.GA1260@google.com> <20111109165201.GI5075@redhat.com> <20111109165925.GC1260@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111109165925.GC1260@google.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 09, 2011 at 08:59:25AM -0800, Tejun Heo wrote: > Freezer depends on the usual "set_current_state(INTERRUPTIBLE); check > freezing; schedule(); check freezing" construct and sends > INTERRUPTIBLE wake up after setting freezing state. The > synchronization hasn't been completely clear but recently been cleaned > up, so as long as freezing condition is tested after INTERRUPTIBLE is > set before going to sleep, the event won't go missing. Just in case, it's scheduled for the next merge window but TIF_FREEZE is gone now. There is freezing() helper which tests all pending freezing conditions and the freezer guarantees there's mb between assertion of freezing() and sending interruptible wakeups to target tasks. Thanks. -- tejun