From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3v6sxG4zsDzDqQ9 for ; Tue, 24 Jan 2017 13:45:38 +1100 (AEDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v0O2iBbm042313 for ; Mon, 23 Jan 2017 21:45:35 -0500 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0b-001b2d01.pphosted.com with ESMTP id 285srk0u63-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 23 Jan 2017 21:45:35 -0500 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 23 Jan 2017 19:45:34 -0700 Date: Mon, 23 Jan 2017 18:45:28 -0800 From: "Paul E. McKenney" To: Michael Ellerman Cc: Ingo Molnar , boqun.feng@linux.vnet.ibm.com, bobby.prani@gmail.com, peterz@infradead.org, fweisbec@gmail.com, dvhart@linux.intel.com, jiangshanlai@gmail.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, josh@joshtriplett.org, dhowells@redhat.com, edumazet@google.com, mathieu.desnoyers@efficios.com, oleg@redhat.com, dipankar@in.ibm.com, will.deacon@arm.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, tglx@linutronix.de Subject: Re: [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering Reply-To: paulmck@linux.vnet.ibm.com References: <20170114091941.GA22961@linux.vnet.ibm.com> <1484385601-23379-2-git-send-email-paulmck@linux.vnet.ibm.com> <20170114093550.GB14970@gmail.com> <20170114195417.GW5238@linux.vnet.ibm.com> <20170114214159.GA7098@linux.vnet.ibm.com> <87efzub3fw.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <87efzub3fw.fsf@concordia.ellerman.id.au> Message-Id: <20170124024528.GG28085@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Jan 23, 2017 at 07:12:03PM +1100, Michael Ellerman wrote: > "Paul E. McKenney" writes: > > > On Sat, Jan 14, 2017 at 11:54:17AM -0800, Paul E. McKenney wrote: > >> On Sat, Jan 14, 2017 at 10:35:50AM +0100, Ingo Molnar wrote: > >> > * Paul E. McKenney wrote: > > > > [ . . . ] > > > >> > > + */ > >> > > +#ifdef CONFIG_PPC > >> > > +#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ > >> > > +#else /* #ifdef CONFIG_PPC */ > >> > > +#define smp_mb__after_unlock_lock() do { } while (0) > >> > > +#endif /* #else #ifdef CONFIG_PPC */ > >> > > >> > Yeah, so I realize that this was pre-existing code, but putting CONFIG_$ARCH > >> > #ifdefs into generic headers is generally frowned upon. > >> > > >> > The canonical approach would be either to define a helper Kconfig variable that > >> > can be set by PPC (but other architectures don't need to set it), or to expose a > >> > suitable macro (function) for architectures to define in their barrier.h arch > >> > header file. > >> > >> Very well, I will add a separate commit for this. 4.11 OK? > > > > Does the patch below seem reasonable? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 271c0601237c41a279f975563e13837bace0df03 > > Author: Paul E. McKenney > > Date: Sat Jan 14 13:32:50 2017 -0800 > > > > rcu: Make arch select smp_mb__after_unlock_lock() strength > > > > The definition of smp_mb__after_unlock_lock() is currently smp_mb() > > for CONFIG_PPC and a no-op otherwise. It would be better to instead > > provide an architecture-selectable Kconfig option, and select the > > strength of smp_mb__after_unlock_lock() based on that option. This > > commit therefore creates CONFIG_ARCH_WEAK_RELACQ, has PPC select it, > > and bases the definition of smp_mb__after_unlock_lock() on this new > > CONFIG_ARCH_WEAK_RELACQ Kconfig option. > > > > Reported-by: Ingo Molnar > > Signed-off-by: Paul E. McKenney > > Cc: Peter Zijlstra > > Cc: Will Deacon > > Cc: Boqun Feng > > Cc: Benjamin Herrenschmidt > > Cc: Paul Mackerras > > Cc: Michael Ellerman > > Cc: > > Personally I'd call it ARCH_WEAK_RELEASE_ACQUIRE, which is longer but > clearer I think. But it's not a big deal, so which ever you prefer. ARCH_WEAK_RELEASE_ACQUIRE it is! > Acked-by: Michael Ellerman Applied, thank you! Thanx, Paul