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 BDFF8C7EE2C for ; Thu, 18 May 2023 11:34:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231209AbjERLee (ORCPT ); Thu, 18 May 2023 07:34:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231124AbjERLea (ORCPT ); Thu, 18 May 2023 07:34:30 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C53DD19B2; Thu, 18 May 2023 04:34:28 -0700 (PDT) Received: from [192.168.2.250] (109-252-144-198.dynamic.spd-mgts.ru [109.252.144.198]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id C504E6605961; Thu, 18 May 2023 12:34:26 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1684409667; bh=QGfLG06H7/U3BYZ2IKDliNOlA1/w+8cf8eGRzQrKSkc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ReEuLbo+ZoRiGPuEqfc355zLJYQLW/j0zJtoZKXX7WJ8tEgE6K/H/+pn7T+EJ6lFi OI3oE0y4fE8XV9Zk8Cv47W/8A381cLjR2o58XCwkcGX3dB6meWTOuu3+dJXwmxB0lP GZsnHQzJoKqlSHV8hiY2NYPvOALtrMsEPr5ZmnvTloTJyoYTusbbOfC7kLfOCyJQK/ zYZZClz9sffjwFVUIXgYiyO5zOAGTfcMSuz7pPhkZogrzPRA26o9hph3b3vHxK+IwW CAiLOyQLCp3qRgHQM8pupTbCFkGEWmpoOFFuHOd+9czl220YX9QnjTwMJXfdnNMVeO bzVptJnCr7dGA== Message-ID: Date: Thu, 18 May 2023 14:34:24 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v6 2/5] i2c: core: run atomic i2c xfer when !preemptible Content-Language: en-US To: Benjamin Bara , Wolfram Sang , Lee Jones , rafael.j.wysocki@intel.com Cc: peterz@infradead.org, jonathanh@nvidia.com, richard.leitner@linux.dev, treding@nvidia.com, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, Benjamin Bara , stable@vger.kernel.org References: <20230327-tegra-pmic-reboot-v6-0-af44a4cd82e9@skidata.com> <20230327-tegra-pmic-reboot-v6-2-af44a4cd82e9@skidata.com> From: Dmitry Osipenko In-Reply-To: <20230327-tegra-pmic-reboot-v6-2-af44a4cd82e9@skidata.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 5/9/23 22:03, Benjamin Bara wrote: > From: Benjamin Bara > > Since bae1d3a05a8b, i2c transfers are non-atomic if preemption is > disabled. However, non-atomic i2c transfers require preemption (e.g. in > wait_for_completion() while waiting for the DMA). > > panic() calls preempt_disable_notrace() before calling > emergency_restart(). Therefore, if an i2c device is used for the > restart, the xfer should be atomic. This avoids warnings like: > > [ 12.667612] WARNING: CPU: 1 PID: 1 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch+0x33c/0x6b0 > [ 12.676926] Voluntary context switch within RCU read-side critical section! > ... > [ 12.742376] schedule_timeout from wait_for_completion_timeout+0x90/0x114 > [ 12.749179] wait_for_completion_timeout from tegra_i2c_wait_completion+0x40/0x70 > ... > [ 12.994527] atomic_notifier_call_chain from machine_restart+0x34/0x58 > [ 13.001050] machine_restart from panic+0x2a8/0x32c > > Use !preemptible() instead, which is basically the same check as > pre-v5.2. > > Fixes: bae1d3a05a8b ("i2c: core: remove use of in_atomic()") > Cc: stable@vger.kernel.org # v5.2+ > Suggested-by: Dmitry Osipenko > Acked-by: Wolfram Sang > Signed-off-by: Benjamin Bara > --- > drivers/i2c/i2c-core.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h > index 1247e6e6e975..05b8b8dfa9bd 100644 > --- a/drivers/i2c/i2c-core.h > +++ b/drivers/i2c/i2c-core.h > @@ -29,7 +29,7 @@ int i2c_dev_irq_from_resources(const struct resource *resources, > */ > static inline bool i2c_in_atomic_xfer_mode(void) > { > - return system_state > SYSTEM_RUNNING && irqs_disabled(); > + return system_state > SYSTEM_RUNNING && !preemptible(); > } > > static inline int __i2c_lock_bus_helper(struct i2c_adapter *adap) > Reviewed-by: Dmitry Osipenko -- Best regards, Dmitry