From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752955AbbIRHA2 (ORCPT ); Fri, 18 Sep 2015 03:00:28 -0400 Received: from h1446028.stratoserver.net ([85.214.92.142]:55141 "EHLO mail.ahsoftware.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752260AbbIRHAB (ORCPT ); Fri, 18 Sep 2015 03:00:01 -0400 Subject: Re: [PATCH 16/16] phy: phy-core: fix initcall level To: Kishon Vijay Abraham I , linux-kernel@vger.kernel.org References: <1440592108-3740-1-git-send-email-holler@ahsoftware.de> <1440592108-3740-17-git-send-email-holler@ahsoftware.de> <55FBAC2D.1020301@ti.com> Cc: linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, Greg KH , Russel King , Andrew Morton , Grant Likely , Tomeu Vizoso From: Alexander Holler Message-ID: <55FBB660.4020302@ahsoftware.de> Date: Fri, 18 Sep 2015 08:59:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <55FBAC2D.1020301@ti.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 18.09.2015 um 08:16 schrieb Kishon Vijay Abraham I: > Hi, > > On Wednesday 26 August 2015 05:58 PM, Alexander Holler wrote: >> The phy-core has to be initialized before other dependent usb-drivers, >> otherwise a crash might occur. >> >> Currently phy_core_init() is called in the initcall-level device, which is >> the same level where most usb-drivers will end up. By luck this seemed to >> have been called most of the time before other usb-drivers without having >> been explicitly enforced. But if phy_core_init() is not called before a >> dependent driver, a null-pointer exception might occur (e.g. because the >> phy device class isn't registered). > > Did you actually face a problem? IIUC the modules get loaded based on > the drivers/Makefile order (unless the other modules are in a different > initcall table). I had a problem while playing with a modified init-system (based on dependencies). So not an actual problem. > IMHO the fix should be in the module that caused the crash. Change it to > use module_init? The problem arises if the init-system ignores the link order and assumes all drivers in the same initcall level can be called without any special ordering. The problem might also appear if a driver changes its name, directory or position in file system. E.g. how to you make sure that a driver in staging will be linked after the phy-core? Actually this happens, but I would assume its by luck. I assume if staging would be renamed to 'beta-quality' a lot of stuff would actually fail because of the problem with the implicit link order. Anyway, nothing which really has to be fixed. It's just a notice that maybe another initcall level of 'subsys' or something else before 'device' might be a better place for phy-core. I've chosen fs_sync instead of subsys because otherwise I would have had to look up if phy-core depends on another subsystem and therefore has to be initialized after subsys. Regards, Alexander Holler > > Thanks > Kishon > >> >> To fix this, phy_core_init() is moved to the initcall-level fs (right >> before the standard initcall level device). >> >> Signed-off-by: Alexander Holler >> --- >> drivers/phy/phy-core.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c >> index fc48fac..4945029 100644 >> --- a/drivers/phy/phy-core.c >> +++ b/drivers/phy/phy-core.c >> @@ -930,7 +930,7 @@ static int __init phy_core_init(void) >> >> return 0; >> } >> -module_init(phy_core_init); >> +fs_initcall_sync(phy_core_init); >> >> static void __exit phy_core_exit(void) >> { >> > -- > 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/ >