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[2620:137:e000::1:20]) by mx.google.com with ESMTP id s184-20020a632cc1000000b004a0dd5c1e54si9507278pgs.108.2023.01.03.01.54.44; Tue, 03 Jan 2023 01:54:58 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=fail (test mode) header.i=@armlinux.org.uk header.s=pandora-2019 header.b="mNrk/czo"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237168AbjACJmo (ORCPT + 99 others); Tue, 3 Jan 2023 04:42:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232970AbjACJmm (ORCPT ); Tue, 3 Jan 2023 04:42:42 -0500 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4918D2D2 for ; Tue, 3 Jan 2023 01:42:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Date:Sender:Message-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:Subject:Cc:To:From:Reply-To:Content-ID :Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To: Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=4fMNHgZDzPHb49xSU4TUscrYEmRUetsr0RmDQrt06rI=; b=mNrk/czourWWRaA79ofmXCfNmP /eYQUwcpOXo0e3atgF/tTg29ftLZxbOJl2rjaBotIrtBedMULRz5kaWblLEEZQRRuyRyPgZcWDBdD VgRUF51F4ZgV9vokiZ0WqFLwVnIoWID7wiLPROknCsAM3usgBzslc/TNzUutRrYDnXVjrKiM9FjQo dwU7YhfRQmvreef1WmtQGyseBrCYI0PSiUaW0RQlaUxLAqwatUxxXxqnzYz0vc1bpuPMXFAcd0DcO 2z6ru8pEYVMQ2navBfm8J0vGJyJU0qFOewO5tuvybMZsLnKxXhnLY0hCUWzHz+yycyMiiOeMuFA3C FasNF7TQ==; Received: from e0022681537dd.dyn.armlinux.org.uk ([fd8f:7570:feb6:1:222:68ff:fe15:37dd]:37962 helo=rmk-PC.armlinux.org.uk) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pCdoZ-0005AA-88; Tue, 03 Jan 2023 09:42:34 +0000 Received: from rmk by rmk-PC.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1pCdoY-0044aT-A5; Tue, 03 Jan 2023 09:42:34 +0000 From: "Russell King (Oracle)" To: Srinivas Kandagatla Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] nvmem: fix registration vs use race MIME-Version: 1.0 Content-Disposition: inline Message-Id: Sender: Russell King Date: Tue, 03 Jan 2023 09:42:34 +0000 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753994702290569762?= X-GMAIL-MSGID: =?utf-8?q?1753994702290569762?= The i.MX6 CPU frequency driver sometimes fails to register at boot time due to nvmem_cell_read_u32() sporadically returning -ENOENT. This happens because there is a window where __nvmem_device_get() in of_nvmem_cell_get() is able to return the nvmem device, but as cells have been setup, nvmem_find_cell_entry_by_node() returns NULL. The occurs because the nvmem core registration code violates one of the fundamental principles of kernel programming: do not publish data structures before their setup is complete. Fix this by making nvmem core code conform with this principle. Signed-off-by: Russell King (Oracle) --- drivers/nvmem/core.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 321d7d63e068..6b89fb6fa582 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -835,22 +835,16 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) nvmem->dev.groups = nvmem_dev_groups; #endif - dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); - - rval = device_register(&nvmem->dev); - if (rval) - goto err_put_device; - if (nvmem->nkeepout) { rval = nvmem_validate_keepouts(nvmem); if (rval) - goto err_device_del; + goto err_put_device; } if (config->compat) { rval = nvmem_sysfs_setup_compat(nvmem, config); if (rval) - goto err_device_del; + goto err_put_device; } if (config->cells) { @@ -867,6 +861,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) if (rval) goto err_remove_cells; + dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); + + rval = device_register(&nvmem->dev); + if (rval) + goto err_remove_cells; + blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem); return nvmem; @@ -876,8 +876,6 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) err_teardown_compat: if (config->compat) nvmem_sysfs_remove_compat(nvmem, config); -err_device_del: - device_del(&nvmem->dev); err_put_device: put_device(&nvmem->dev);