Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753599AbbBSBTh (ORCPT ); Wed, 18 Feb 2015 20:19:37 -0500 Received: from mail-ob0-f180.google.com ([209.85.214.180]:39027 "EHLO mail-ob0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752136AbbBSBTf (ORCPT ); Wed, 18 Feb 2015 20:19:35 -0500 MIME-Version: 1.0 In-Reply-To: <87vbiysv1v.fsf@rustcorp.com.au> References: <1424177796-17923-1-git-send-email-harish_kandiga@mentor.com> <874mqjuaky.fsf@rustcorp.com.au> <87vbiysv1v.fsf@rustcorp.com.au> From: Lucas De Marchi Date: Wed, 18 Feb 2015 23:19:14 -0200 Message-ID: Subject: Re: [PATCH] libkmod-module: Remove directory existence check for KMOD_MODULE_BUILTIN To: Rusty Russell Cc: Harish Jenny K N , linux-modules , lkml , greg KH Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2306 Lines: 54 On Wed, Feb 18, 2015 at 8:40 PM, Rusty Russell wrote: > Lucas De Marchi writes: >> On Wed, Feb 18, 2015 at 2:07 AM, Rusty Russell wrote: >> Yeah, I just thought (an wanted that) the attributes were being >> created first and then hooked up in the sysfs tree under >> /sys/module/. I.e. if the directory exists and there's no >> initstate this is because it's a builtin module. I don't want to >> wait/sleep on the file to appear because users of >> kmod_module_get_initstate() may not tolerate this behavior. >> >> Looking up at the old module-init-tools, it used an ugly loop with >> usleep() before trying to read the file again :-/ >> >> Can we change kernel side guaranteeing the initstate file appears >> together with the directory? > > Greg? The core problem is that kmod looks for > /sys/module//initstate; if it's not there, it assumes a builtin > module. Just to make it clear: We try to open /sys/module//initstate. If it fails we stat /sys/module/ checking if it exists and is a directory. If it does then we assume the module is builtin. > However, this is racy when a module is being inserted. Is there a way > to create this sysfs file and dir atomically? Greg, the question is still valid since it'd be nice to have this guarantee and be able to correctly reply the state with whatever is in initstate file, but... Rusty, thinking again if we fallback to "coming" instead of "builtin" everything should be fine, no? Because the decision about builtin has already been taken by looking at the modules.builtin index. If we return "coming" here the second call to modprobe would call init_module() again which would wait for the first one to complete (or return EEXIST if it's already live) since we only shortcut the init_module() call if the module is live or builtin what do you think? Harrish, in your patch if you just change the "return KMOD_MODULE_BUILTIN;" to "return KMOD_MODULE_COMING;" does it work? -- Lucas De Marchi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/