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Date: Thu, 7 Feb 2019 20:11:10 +0100 From: "Rafael J. Wysocki" <rafael@...nel.org> To: Lukas Wunner <lukas@...ner.de> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, LKML <linux-kernel@...r.kernel.org>, Linux PM <linux-pm@...r.kernel.org>, Ulf Hansson <ulf.hansson@...aro.org>, Daniel Vetter <daniel@...ll.ch>, Andrzej Hajda <a.hajda@...sung.com>, Russell King - ARM Linux <linux@...linux.org.uk>, Lucas Stach <l.stach@...gutronix.de>, Linus Walleij <linus.walleij@...aro.org>, Thierry Reding <thierry.reding@...il.com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Joerg Roedel <jroedel@...e.de> Subject: Re: [PATCH v2 2/9] driver core: Avoid careless re-use of existing device links On Thu, Feb 7, 2019 at 8:03 PM Lukas Wunner <lukas@...ner.de> wrote: > > Sorry, late to the party. > > On Fri, Feb 01, 2019 at 01:46:54AM +0100, Rafael J. Wysocki wrote: > > After commit ead18c23c263 ("driver core: Introduce device links > > reference counting"), if there is a link between the given supplier > > and the given consumer already, device_link_add() will refcount it > > and return it unconditionally. However, if the flags passed to > > it on the second (or any subsequent) attempt to create a device > > link between the same consumer-supplier pair are not compatible with > > the existing link's flags, that is incorrect. > > Prior to ead18c23c263, a second invocation of device_link_add() also > returned the existing device link without checking for incompatible > flags. Hence this issue was not introduced by ead18c23c263, but > rather by 9ed9895370ae ("driver core: Functional dependencies tracking > support"), i.e. it was present all along. (Unless I'm missing something.) > > > > Moreover, if the DL_FLAG_AUTOREMOVE_CONSUMER flag is passed to > > device_link_add(), its caller will expect its reference to the link > > to be dropped automatically on consumer driver removal, which will > > not happen if that flag is not set in the link's flags (and > > analogously for DL_FLAG_AUTOREMOVE_SUPPLIER). For this reason, make > > device_link_add() update the existing link's flags accordingly > > before returning it to the caller. > > Same here. > > > > Fixes: ead18c23c263 ("driver core: Introduce device links reference counting") > > Should rather be > Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support") > > (Again, unless I'm missing something.) I haven't checked far enough into the past, sorry about that. You are right, but actually I think that Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support") should be there in addition to the other Fixes: tag, because the issue is still present after that commit and the patch does not apply directly on top of 9ed9895370ae.
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