Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752486AbaA2OzY (ORCPT ); Wed, 29 Jan 2014 09:55:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:11188 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752080AbaA2OzX (ORCPT ); Wed, 29 Jan 2014 09:55:23 -0500 Date: Wed, 29 Jan 2014 15:55:35 +0100 From: Oleg Nesterov To: Rakib Mullick Cc: LKML , Ingo Molnar , Andrew Morton Subject: Re: Do we really need curr_target in signal_struct ? Message-ID: <20140129145535.GA12562@redhat.com> References: <1390895840.8373.2.camel@beeld> <20140128164320.GB7596@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/29, Rakib Mullick wrote: > > On Tue, Jan 28, 2014 at 10:43 PM, Oleg Nesterov wrote: > > > But I guess ->curr_target was added exactly to avoid this loop if > > possible, assuming that wants_signal(->current_targer) should be > > likely true. Although perhaps this optimization is too simple. > > > Well, this code block will only hit when first check for wants_signal() > will miss, Yes, > that means we need to find some other thread of the group. Yes, > AFAIU, ->current_target is only a loop breaker to avoid infinite loop, No. It caches the last result of "find a thread which can handle this group-wide signal". > but - by using while_each_thread() we can remove it completely, thus > helps to get rid from maintaining it too. ... and remove the optimization above. > I'll prepare a proper patch with you suggestions for reviewing. I am not sure we want this patch. Once again, I do not know how much ->curr_target helps, and certainaly it can't help always. But you should not blindly remove it just because yes, sure, it is not strictly needed to find a wants_signal() thread. Oleg. -- 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/