From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756297AbcCWR32 (ORCPT ); Wed, 23 Mar 2016 13:29:28 -0400 Received: from mail-bn1on0084.outbound.protection.outlook.com ([157.56.110.84]:6687 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755488AbcCWR30 (ORCPT ); Wed, 23 Mar 2016 13:29:26 -0400 Authentication-Results: the-dreams.de; dkim=none (message not signed) header.d=none;the-dreams.de; dmarc=none action=none header.from=caviumnetworks.com; Date: Wed, 23 Mar 2016 18:29:05 +0100 From: Jan Glauber To: Wolfram Sang CC: , Subject: Re: [PATCH] i2c: Prevent endless uevent loop with dev_dbg Message-ID: <20160323172905.GB1712@hardcore> References: <1458748247-9219-1-git-send-email-jglauber@cavium.com> <20160323165033.GB1385@katana> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160323165033.GB1385@katana> User-Agent: Mutt/1.5.21 (2010-09-15) X-Originating-IP: [109.193.46.245] X-ClientProxiedBy: HE1PR05CA0024.eurprd05.prod.outlook.com (25.162.181.34) To SN2PR0701MB768.namprd07.prod.outlook.com (25.160.15.146) X-MS-Office365-Filtering-Correlation-Id: 1006d662-9def-4343-99ca-08d35340ad50 X-Microsoft-Exchange-Diagnostics: 1;SN2PR0701MB768;2:8fN9RVoTdrlURsdJFXLqfJFRUQAWVQ5+D2ITB1y1Cjrq2AoRxGKQhde+/sstK8UXNdFwg+lumhYDc7jA6o9pl4xUMAcMt8FpWq0watcIoXSXOKGEaZ8oRQuuEY0UHXlisKHVbLEr4loVsfS96BBQ17kBKdhVWqefoCqT8ofJ8Z1DOXptzuOy8C1JtLyKiC5V;3:auiKxWiIeFXXh7URkU49eODf8PiggMWjRYgvfQvu+c4reH4gaIxemsYkwn5JZfI77qF1Svz7iB/xYrYz8tbgHQJL5UlNJX/R2vr/EIqmuSzyt6UB3p32g8A5qvUPd43A;25: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 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:SN2PR0701MB768; 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X-Microsoft-Exchange-Diagnostics: 1;SN2PR0701MB768;23: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 X-Microsoft-Exchange-Diagnostics: 1;SN2PR0701MB768;5:REWCp8rFXJ8jRe44mwkY2/SJgSnIh3+xJsTuLZ+wzGBQh7SVo7tOkGrQTqwQoGr4kr9zJDf6PT8ONU/9A9asVBFnpytBBI+YNssgaBGm98t4FPkBoMl+ucaN0kyRbdTIQ6iBxJv4yy5HxVL2k7wshw==;24:exg8G31ja58fUX3EKCEpkffYLlStUxlAoIw6pRR6kJ/ISo/JDpkLnibB4xyeMJpeXwKTOaazN4DXaztZeROJzmu6o5kEG4fU6uAIYMxsmT8= SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: caviumnetworks.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Mar 2016 17:29:22.9812 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN2PR0701MB768 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 23, 2016 at 05:50:33PM +0100, Wolfram Sang wrote: > On Wed, Mar 23, 2016 at 04:50:47PM +0100, Jan Glauber wrote: > > After enabling CONFIG_I2C_DEBUG_CORE my system was broken > > (no network, console login not possible). System log was > > flooded with the this message: > > > > ... > > [ 608.052077] rtc-ds1307 0-0068: uevent > > [ 608.052500] rtc-ds1307 0-0068: uevent > > [ 608.052925] rtc-ds1307 0-0068: uevent > > ... > > > > The culprit is the dev_dbg printk in the i2c uevent handler. > > If this is activated (for instance by CONFIG_I2C_DEBUG_CORE) > > it results in an endless loop with systemd-journald. > > > > This happens if user-space scans the system log and reads the uevent > > file to get information about a newly created device, which seems fair > > use to me. Unfortunately reading the "uevent" file uses the same > > function that runs for creating the uevent for a new device, > > generating the next syslog entry. > > > > Ideally user-space would implement a recursion detection and > > after reading the same device file for the 1000th time call it a > > day, but nevertheless I think we should avoid this problem by > > removing the debug print completly or using another print variant. > > Thanks for pointing out this problem. I think this debug can go. I also > think the function can be cleaned up some more. Can you test this patch? Works for me! Thanks, Jan > Thanks, > > Wolfram > > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c > index 0f2f8484e8ec1f..e584d88ee337f6 100644 > --- a/drivers/i2c/i2c-core.c > +++ b/drivers/i2c/i2c-core.c > @@ -525,22 +525,16 @@ static int i2c_device_match(struct device *dev, struct device_driver *drv) > return 0; > } > > - > -/* uevent helps with hotplug: modprobe -q $(MODALIAS) */ > static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env) > { > - struct i2c_client *client = to_i2c_client(dev); > + struct i2c_client *client = to_i2c_client(dev); > int rc; > > rc = acpi_device_uevent_modalias(dev, env); > if (rc != -ENODEV) > return rc; > > - if (add_uevent_var(env, "MODALIAS=%s%s", > - I2C_MODULE_PREFIX, client->name)) > - return -ENOMEM; > - dev_dbg(dev, "uevent\n"); > - return 0; > + return add_uevent_var(env, "MODALIAS=%s%s", I2C_MODULE_PREFIX, client->name); > } > > /* i2c bus recovery routines */ >