From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751248AbXAIKJj (ORCPT ); Tue, 9 Jan 2007 05:09:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751256AbXAIKJj (ORCPT ); Tue, 9 Jan 2007 05:09:39 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:59319 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751248AbXAIKJi (ORCPT ); Tue, 9 Jan 2007 05:09:38 -0500 Date: Tue, 9 Jan 2007 15:39:26 +0530 From: Srivatsa Vaddagiri To: Andrew Morton Cc: Oleg Nesterov , David Howells , Christoph Hellwig , Ingo Molnar , Linus Torvalds , linux-kernel@vger.kernel.org, Gautham shenoy Subject: Re: [PATCH] flush_cpu_workqueue: don't flush an empty ->worklist Message-ID: <20070109100925.GA22080@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20070106163851.GA13579@in.ibm.com> <20070106111117.54bb2307.akpm@osdl.org> <20070107110013.GD13579@in.ibm.com> <20070107115957.6080aa08.akpm@osdl.org> <20070107210139.GA2332@tv-sign.ru> <20070108155428.d76f3b73.akpm@osdl.org> <20070109050417.GC589@in.ibm.com> <20070108212656.ca77a3ba.akpm@osdl.org> <20070109093302.GE589@in.ibm.com> <20070109015152.d5021254.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070109015152.d5021254.akpm@osdl.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 09, 2007 at 01:51:52AM -0800, Andrew Morton wrote: > > This thread makes absolutely -no- calls to try_to_freeze() in its lifetime. > > Looks like a bug to me. powerpc does appear to try to support the freezer. > > > 1. Does this mean that the thread can't be frozen? (lets say that the > > thread's PF_NOFREEZE is not set) > > yup. I'd expect the freeze_processes() call would fail if this thread is > running. ok. > > > AFAICS it can still be frozen by sending it a signal and have the signal > > delivery code call try_to_freeze() .. > > kernel threads don't take signals in the same manner as userspace. A > kernel thread needs to explicitly poll, via > > if (signal_pending(current)) > do_something() Thanks for the education! I feel much better about the use of process freezer now .. > > 2. If the thread can be frozen at any arbitrary point of its execution, then I > > dont see what prevents cpu_online_map from changing under the feet of rtasd > > thread, > > It cannot. Excellent .. I just hope the latency of freeze_processes() is tolerable .. -- Regards, vatsa