From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 123116B0033 for ; Mon, 23 Oct 2017 06:27:54 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id g10so8552719wrg.6 for ; Mon, 23 Oct 2017 03:27:54 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id f17si5143646wrc.29.2017.10.23.03.27.52 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 23 Oct 2017 03:27:53 -0700 (PDT) Date: Mon, 23 Oct 2017 12:26:47 +0200 (CEST) From: Thomas Gleixner Subject: RE: [PATCH 01/15] sched: convert sighand_struct.count to refcount_t In-Reply-To: <2236FBA76BA1254E88B949DDB74E612B802B4359@IRSMSX102.ger.corp.intel.com> Message-ID: References: <1508501757-15784-1-git-send-email-elena.reshetova@intel.com> <1508501757-15784-2-git-send-email-elena.reshetova@intel.com> <2236FBA76BA1254E88B949DDB74E612B802B4359@IRSMSX102.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: "Reshetova, Elena" Cc: "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "peterz@infradead.org" , "gregkh@linuxfoundation.org" , "viro@zeniv.linux.org.uk" , "tj@kernel.org" , "hannes@cmpxchg.org" , "lizefan@huawei.com" , "acme@kernel.org" , "alexander.shishkin@linux.intel.com" , "eparis@redhat.com" , "akpm@linux-foundation.org" , "arnd@arndb.de" , "luto@kernel.org" , "keescook@chromium.org" , "dvhart@infradead.org" , "ebiederm@xmission.com" , "linux-mm@kvack.org" , "axboe@kernel.dk" On Mon, 23 Oct 2017, Reshetova, Elena wrote: > > On Fri, 20 Oct 2017, Elena Reshetova wrote: > > How did you make sure that these atomic operations have no other > > serialization effect and can be replaced with refcount? > > What serialization effects? Are you taking about smth else than memory > ordering? Well, the memory ordering constraints can be part of serialization mechanisms. Unfortunately they are not well documented .... > For memory ordering my current hope is that we can just make refcount_t > to use same strict atomic primitives and then it would not make any > difference. I think this would be the simplest way for everyone since I > think even some maintainers are having issues understanding all the > implications of "relaxed" ordering. Well, that would make indeed the conversion simpler because then it is just a drop in replacement. Albeit there might be some places which benefit of the relaxed ordering as on some architectures strict ordering is expensive. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org