Path: csiph.com!aioe.org!news.servidellagleba.it!bofh.it!news.nic.it!robomod From: Peter Zijlstra Newsgroups: linux.kernel Subject: Re: [PATCH tip/core/rcu 07/13] rcu: Add smp_mb__after_atomic() to sync_exp_work_done() Date: Thu, 13 Apr 2017 11:20:02 +0200 Message-ID: References: Dkim-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=afxel/oMStr8W2XCG5smOTz33o3UjUQXGB5TG2lUdwY=; b=CRGJxJvlzXq9tBWkMF6uIzRnv wcNVNCLsN/FIQv+IRmdXWiZN4PRkchMvVsDRcygjFk5Y5Oh1d50OOq8/SNgch4VjVn3H27JWSx8M8 k1uT1RGc1mjlH2ubzYF5hmWvAcQRj7MFV82PjsylEcv4u310COtkpL7fMogeRQ3kb8qBmSGnJJXBy ZaTpjWDNzlkTsPz8BmQ09Y+EApuTY3tGDFpKZnYTtlQ5BpDx9hnW/Iq32J63X8FPLSQgQchHuDJ13 6lxnxLvKKJreJGKs95o3gHzxsZX5h9mEHysZsikvfX4LIsTFasxBAPpMCvSKFaWjen3UEi7Qzlrdv AqoUsXZTg==; MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20170113 (1.7.2) Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 11 Organization: linux.* mail to news gateway X-Original-Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com X-Original-Date: Thu, 13 Apr 2017 11:18:32 +0200 X-Original-Message-ID: <20170413091832.phnfppqjjy6sislo@hirez.programming.kicks-ass.net> X-Original-References: <20170412165441.GA17149@linux.vnet.ibm.com> <1492016149-18834-7-git-send-email-paulmck@linux.vnet.ibm.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1622844 On Wed, Apr 12, 2017 at 09:55:43AM -0700, Paul E. McKenney wrote: > However, a little future-proofing is a good thing, > especially given that smp_mb__before_atomic() is only required to > provide acquire semantics rather than full ordering. This commit > therefore adds smp_mb__after_atomic() after the atomic_long_inc() > in sync_exp_work_done(). Oh!? As far as I'm away the smp_mb__{before,after}_atomic() really must provide full MB, no confusion about that. We have other primitives for acquire/release.