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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 2DE85C433FE for ; Thu, 3 Dec 2020 15:54:17 +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 B574A207AA for ; Thu, 3 Dec 2020 15:54:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B574A207AA 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:MIME-Version:Message-ID:Date:In-reply-to:Subject:To: From:References:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=otZiv3nelG6oulgLlZbI5GX6WwnLlTfeqMBa8jOIduQ=; b=NCq0lW/TNLoZ8c6WKh54tJzjz fsISlVpsPq6vNK/Jt7235b1KrLiLKSepTMReAA3RhN8c1yO/z1F3+0DPrpMRoWZdsfYmSqLcFRB/P 4PEFKqkIchJN36uq3yCmp807vs32Ejx6YYUhU7l7+cV0KzffyXrwyEscUqdD/gTwvY5GqCxSjKlPp PoxQAVIAPViJI2QqG1uTGRJG3+20Kya7YCiIlG4nUZ36lVYtTUDZub12HW7owifpwnoGDX0gSAHi4 76pibD2kFAqHHWeSOj4CK5/mW2d1/tRirYlLaynjMKAZONaCPoTB+rMvyiXhSA3h7q95qCQDjhTSE DYRL4bGtg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkquk-0002oX-QN; Thu, 03 Dec 2020 15:53:02 +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 1kkquh-0002ne-NY for linux-arm-kernel@lists.infradead.org; Thu, 03 Dec 2020 15:53:00 +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 AFA4B11D4; Thu, 3 Dec 2020 07:52:55 -0800 (PST) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5BF663F575; Thu, 3 Dec 2020 07:52:49 -0800 (PST) References: <20201124141449.572446-1-maz@kernel.org> <20201124141449.572446-3-maz@kernel.org> <20201203130320.GQ3021@hirez.programming.kicks-ass.net> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Peter Zijlstra Subject: Re: [PATCH v2 2/6] genirq: Allow an interrupt to be marked as 'raw' In-reply-to: <20201203130320.GQ3021@hirez.programming.kicks-ass.net> Date: Thu, 03 Dec 2020 15:52:44 +0000 Message-ID: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201203_105259_821431_A2DAC9D9 X-CRM114-Status: GOOD ( 11.81 ) 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: Mark Rutland , Android Kernel Team , Russell King , Marc Zyngier , linux-kernel , Catalin Marinas , Thomas Gleixner , Will Deacon , LAK 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 03/12/20 13:03, Peter Zijlstra wrote: > On Thu, Nov 26, 2020 at 06:18:33PM +0000, Valentin Schneider wrote: >> If I got the RCU bits right from what Thomas mentioned in >> >> https://lore.kernel.org/r/87ft5q18qs.fsf@nanos.tec.linutronix.de >> https://lore.kernel.org/r/87lfewnmdz.fsf@nanos.tec.linutronix.de >> >> then we're still missing something to notify RCU in the case the IRQ hits >> the idle task. All I see on our entry path is >> >> trace_hardirqs_off(); >> ... >> irq_handler() >> handle_domain_irq(); >> ... >> trace_hardirqs_on(); >> >> so we do currently rely on handle_domain_irq()'s irq_enter() + irq_exit() >> for that. rcu_irq_enter() says CONFIG_RCU_EQS_DEBUG=y can detect missing >> bits, but I don't get any warnings with your series on my Juno. > > The scheduler IPI really doesn't need RCU either ;-) Because it doesn't enter any new read-side section, right? But as with any other interrupt, we could then go through: preempt_schedule_irq() ~> pick_next_task_fair() -> newidle_balance() which does enter a read-side section, so RCU would need to be watching. Looking at kernel/entry/common.c:irqentry_exit_cond_resched(), it seems we do check for this via rcu_irq_exit_check_preempt(). I however cannot grok why irqentry_exit() *doesn't* call into preempt_schedule_irq() if RCU wasn't watching on IRQ entry, so I'm starting to question everything (again). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel