From patchwork Tue Jan 3 09:42:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Russell King (Oracle)" X-Patchwork-Id: 13087533 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1F499C3DA7D for ; Tue, 3 Jan 2023 14:45:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Date:Message-Id: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-Owner; bh=qc0X5bVdB/bI9kHjhFOGJx/yB699yhhTqxOdnFH7ZIU=; b=INf1RQlSlCs9U3 hgtkI9JL25Z9a0jkvXXpjn4esW4CZwjIOmzhNuYLKbU8DVH9D88yPbQt14ZDnJWWCTJGO6HXSIh+6 ZAhPD6OjnihEzopxfxK9A9yoVCR9i4v3swKiEoN7QK6CF8SqIwEcvE6KAgD6z8gKqESr+54YDa3qT JpwlyeaEmhVrA0AMcttU1blxJkHbUgT4kij0c1MJtg6ikURbflUd4QfG0ESDKy0h8ONaUJEShKlam kuLye4YL4oq8yk+TP/bVUQPLyXkuBe3qa7FSuSyii221nVvXkNR1rJA7YPmqGjUNan5Puh6vhTEHU JleqJX1EtKsKCylg8wQw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pCiVZ-0025D7-Dk; Tue, 03 Jan 2023 14:43:18 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pCdqe-000VQK-Vj for linux-arm-kernel@lists.infradead.org; Tue, 03 Jan 2023 09:44:49 +0000 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: Date: Tue, 03 Jan 2023 09:42:34 +0000 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230103_014445_088388_97F0CA97 X-CRM114-Status: GOOD ( 13.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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);