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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBE37C433F5 for ; Sat, 19 Feb 2022 09:56:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240555AbiBSJ4x (ORCPT ); Sat, 19 Feb 2022 04:56:53 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:53396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232848AbiBSJ4u (ORCPT ); Sat, 19 Feb 2022 04:56:50 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FD7F38A2 for ; Sat, 19 Feb 2022 01:56:31 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 34477B8013C for ; Sat, 19 Feb 2022 09:56:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA9AFC004E1; Sat, 19 Feb 2022 09:56:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645264589; bh=oE4n057itlw6z2EKGJmIYQhY6E/5y7x1AOT0/sQpMMI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=g0lbhpjjGxWweCjUcNJUB522eW0PRgXADI9p1QWopi1qyAUDziM0YvIHnmtwv28hS VPlj16C6Iyo9Fke4PtPLvQxCH4cGKjM55z9p/EgEMldmovrjLO3/SlNM5rcinXAfHU M+M6m2OIP2Yya0bqO4D7jT110e523sZs4r351y1XZV+p/O0Nquwm4NGl13F+JWpMKX I97lemeyEmOPK60gXRdqK70FY8bBw6Ctk5G+5wnJ1i3qXpPjesC71ZI5h/S0WE0lHR /4ABvTPJHuFaVYM52dkGnaYBnmUjE2/Tyb0OZYQCl3Vh5SQMh1hTCBQU5oDRc3+rHT Sh+8ztvWZDWgg== Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nLMTa-008xLf-WF; Sat, 19 Feb 2022 09:56:27 +0000 MIME-Version: 1.0 Date: Sat, 19 Feb 2022 09:56:26 +0000 From: Marc Zyngier To: Barry Song <21cnbao@gmail.com> Cc: tglx@linutronix.de, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com, Barry Song Subject: Re: [PATCH] irqchip/gic-v3: use dsb(ishst) to synchronize data to smp before issuing ipi In-Reply-To: <20220218215549.4274-1-song.bao.hua@hisilicon.com> References: <20220218215549.4274-1-song.bao.hua@hisilicon.com> User-Agent: Roundcube Webmail/1.4.13 Message-ID: <6432e7e97b828d887da8794c150161c4@kernel.org> X-Sender: maz@kernel.org Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: 21cnbao@gmail.com, tglx@linutronix.de, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com, song.bao.hua@hisilicon.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-02-18 21:55, Barry Song wrote: > dsb(ishst) should be enough here as we only need to guarantee the > visibility of data to other CPUs in smp inner domain before we > send the ipi. > > Signed-off-by: Barry Song > --- > drivers/irqchip/irq-gic-v3.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/irqchip/irq-gic-v3.c > b/drivers/irqchip/irq-gic-v3.c > index 5e935d97207d..0efe1a9a9f3b 100644 > --- a/drivers/irqchip/irq-gic-v3.c > +++ b/drivers/irqchip/irq-gic-v3.c > @@ -1211,7 +1211,7 @@ static void gic_ipi_send_mask(struct irq_data > *d, const struct cpumask *mask) > * Ensure that stores to Normal memory are visible to the > * other CPUs before issuing the IPI. > */ > - wmb(); > + dsb(ishst); > > for_each_cpu(cpu, mask) { > u64 cluster_id = MPIDR_TO_SGI_CLUSTER_ID(cpu_logical_map(cpu)); I'm not opposed to that change, but I'm pretty curious whether this makes any visible difference in practice. Could you measure the effect of this change for any sort of IPI heavy workload? Thanks, M. -- Jazz is not dead. It just smells funny...