Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756996Ab1ERPrd (ORCPT ); Wed, 18 May 2011 11:47:33 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:48975 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756941Ab1ERPrb convert rfc822-to-8bit (ORCPT ); Wed, 18 May 2011 11:47:31 -0400 MIME-Version: 1.0 In-Reply-To: References: <20110517.134312.226762699.davem@davemloft.net> <1305732459_6563@mail4.comsite.net> From: Grant Likely Date: Wed, 18 May 2011 09:47:10 -0600 X-Google-Sender-Auth: zmkfP4E_2q0shl0p2NmSMIdZHUM Message-ID: Subject: Re: [PATCH] of: fix race when matching drivers To: Milton Miller Cc: David Miller , devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, Linus Torvalds Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2230 Lines: 49 [cc'ing Linus: This is fix for a 2.6.39 regression, so just a heads up that I'll be sending you a pull req ASAP (later this morning)] On Wed, May 18, 2011 at 9:41 AM, Grant Likely wrote: > On Wed, May 18, 2011 at 9:27 AM, Milton Miller wrote: >> If two drivers are probing devices at the same time, both will write >> their match table result to the dev->of_match cache at the same time. >> >> Only write the result if the device matches. >> >> In a thread titled "SBus devices sometimes detected, sometimes not", >> Meelis reported his SBus hme was not detected about 50% of the time. >> From the debug suggested by Grant it was obvious another driver matched >> some devices between the call to match the hme and the hme discovery >> failling. >> >> Reported-by: Meelis Roos >> Signed-off-by: Milton Miller >> --- >> >> Grant, I really think this of_match cache in the device node is bad a >> bad tradeoff, and am willing to submit patches to remove it for 2.6.40. >> It is only used by about 26 drivers and all use it once during probe >> to fill out their driver data. ?It comes at the cost of a long for >> every struct device in every system. > > Ah, bugger. ?I had /thought/ that matching and probing were kept > together with a mutex. ?So, yes, this is bad and the of_match needs to > be removed. ?Thanks for volunteering to submit the patch. ?It should > be backported to 2.6.39 too. > >> I'll even offer to throw in a patch to cache the parsing of the >> compatible property to speed up of_device_is_compatible if needed. > > That would be useful. ?:-) > > I'll pick up your patch right now and fire it off to Linus. ... it's not perfect since it will break some theoretical drivers unbind/rebind use-cases, but I cannot think of any actual examples, and it is far safer than the current code. Regardless, the removal of of_match will definitely need to go into stable when it is ready. g. -- 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/