From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5BFBC433E0 for ; Mon, 10 Aug 2020 12:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8DA5F2073A for ; Mon, 10 Aug 2020 12:05:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726542AbgHJMFn convert rfc822-to-8bit (ORCPT ); Mon, 10 Aug 2020 08:05:43 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:54053 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726141AbgHJMFn (ORCPT ); Mon, 10 Aug 2020 08:05:43 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-230-tvWpWrCcO7y7IVQQWcjw3Q-1; Mon, 10 Aug 2020 13:05:39 +0100 X-MC-Unique: tvWpWrCcO7y7IVQQWcjw3Q-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 10 Aug 2020 13:05:38 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 10 Aug 2020 13:05:38 +0100 From: David Laight To: "'peterz@infradead.org'" , Steven Rostedt CC: "tglx@linutronix.de" , "mingo@kernel.org" , "will@kernel.org" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "elver@google.com" , "paulmck@kernel.org" , "rjw@rjwysocki.net" Subject: RE: [RFC][PATCH 2/3] locking,entry: #PF vs TRACE_IRQFLAGS Thread-Topic: [RFC][PATCH 2/3] locking,entry: #PF vs TRACE_IRQFLAGS Thread-Index: AQHWbw1/Z8lTQlAHP0ywRZaHVLPEDKkxPiFg Date: Mon, 10 Aug 2020 12:05:38 +0000 Message-ID: References: <20200807192336.405068898@infradead.org> <20200807193018.060388629@infradead.org> <20200807162148.48d96247@oasis.local.home> <20200810115743.GU2674@hirez.programming.kicks-ass.net> In-Reply-To: <20200810115743.GU2674@hirez.programming.kicks-ass.net> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: peterz@infradead.org > Sent: 10 August 2020 12:58 > ... > > > --- a/include/linux/entry-common.h > > > +++ b/include/linux/entry-common.h > > > @@ -310,6 +310,7 @@ void irqentry_exit_to_user_mode(struct p > > > #ifndef irqentry_state > > > typedef struct irqentry_state { > > > bool exit_rcu; > > > + bool irqs_enabled; > > > > Instead of passing a structure around, should we look at converting > > "irqentry_state" into a flags field? > > Probably, on x86_64-linux sizeof(_Bool) == 1, so it's two bytes and that > fits perfectly fine in a normal return value, but yeah, this is common > code now and we can't rely on sizeof(_Bool) being sane. I'd check the arm ABI(s). IIRC 'sizeof bool' changed - but I can't remember which way :-) There are probably other ABI where a 'struct' return value is always implemented as a 'pass by reference' parameter (Probably M68k?). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)