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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 C49F5C388F7 for ; Fri, 13 Nov 2020 16:59:27 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 59F25217A0 for ; Fri, 13 Nov 2020 16:59:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gpd/9Cxn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59F25217A0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FR2QS9XJcJUOUQs8YVuXwgyT3eHgXoF2vTQRoezT3jo=; b=gpd/9CxnM+6hY5aL/1r+etLtu 3pM+3l+xpXTYy8Dr82LTqzNViIv187IFgUuqXE8Vp7aDoXriS4HA5Ny7uXbh93tA+jJ537G6MvfF1 ClJQHWiZLdAc9BeMp8kn77xSkNQz/v48cOt64Qk2PHTVXYZVkMvCimGytoe3wNAZRl7qW1ue5K+2Y mhbsmopNIQ7Orae+ab+VSFPpOOyyF1M6tL8gl/+Jx5zcvb3HVQU12d3zwNshXyfje1QYCRpcRGJHy +fZsIEf7To8OJd4v5xXCCGv0VOQsEVDPjVtB0j/EoLkCb5CtrRrpiWz04yOkjh223FHoSVbETkB8x SDirKS/bQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kdcPR-00087t-NU; Fri, 13 Nov 2020 16:58:49 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kdcPO-00086u-Js for linux-arm-kernel@lists.infradead.org; Fri, 13 Nov 2020 16:58:47 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 08F511042; Fri, 13 Nov 2020 08:58:45 -0800 (PST) Received: from localhost (unknown [10.1.198.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9EB273F718; Fri, 13 Nov 2020 08:58:44 -0800 (PST) Date: Fri, 13 Nov 2020 16:58:43 +0000 From: Ionela Voinescu To: Mark Rutland Subject: Re: [PATCH] arm64: abort counter_read_on_cpu() when irqs_disabled() Message-ID: <20201113165843.GA6973@arm.com> References: <20201106125334.21570-1-ionela.voinescu@arm.com> <20201113155328.4194-1-ionela.voinescu@arm.com> <20201113160234.GB44988@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201113160234.GB44988@C02TD0UTHF1T.local> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201113_115846_732601_054F657F X-CRM114-Status: GOOD ( 25.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: catalin.marinas@arm.com, linux-kernel@vger.kernel.org, sudeep.holla@arm.com, will@kernel.org, morten.rasmussen@arm.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Friday 13 Nov 2020 at 16:02:34 (+0000), Mark Rutland wrote: > On Fri, Nov 13, 2020 at 03:53:28PM +0000, Ionela Voinescu wrote: > > Given that smp_call_function_single() can deadlock when interrupts are > > disabled, abort the SMP call if irqs_disabled(). This scenario is > > currently not possible given the function's uses, but safeguard this for > > potential future uses. > > Sorry to contradict earlier feedback, but I think this is preferable > as-is, since smp_call_function_single() will > WARN_ON_ONCE(irqs_disabled())), but this will silently mask any dodgy > usage. Probably it only contradicts the chosen implementation. > > If we want a separate check here, I reckon we should wrap it with a > WARN_ON_ONCE(), and only relax that if/when we have a legitimate case > for calling this with IRQs disabled. > That's fair. I'll replace the condition below with: if (!cpu_has_amu_feat(cpu)) return -EOPNOTSUPP; if (WARN_ON_ONCE(irqs_disabled()) return -EPERM; Thanks for your time, Ionela. > Thanks, > Mark. > > > > > Signed-off-by: Ionela Voinescu > > Cc: Catalin Marinas > > Cc: Will Deacon > > --- > > arch/arm64/kernel/topology.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > > index 3a083a9a8ef2..e387188741f2 100644 > > --- a/arch/arm64/kernel/topology.c > > +++ b/arch/arm64/kernel/topology.c > > @@ -343,7 +343,11 @@ static void cpu_read_constcnt(void *val) > > static inline > > int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val) > > { > > - if (!cpu_has_amu_feat(cpu)) > > + /* > > + * Abort call on counterless CPU or when interrupts are > > + * disabled - can lead to deadlock in smp sync call. > > + */ > > + if (!cpu_has_amu_feat(cpu) || unlikely(irqs_disabled())) > > return -EOPNOTSUPP; > > > > smp_call_function_single(cpu, func, val, 1); > > -- > > 2.17.1 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel