From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751782AbeBTNNA (ORCPT ); Tue, 20 Feb 2018 08:13:00 -0500 Received: from merlin.infradead.org ([205.233.59.134]:55754 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751587AbeBTNM7 (ORCPT ); Tue, 20 Feb 2018 08:12:59 -0500 Date: Tue, 20 Feb 2018 14:12:53 +0100 From: Peter Zijlstra To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] locking/ww_mutex: add ww_mutex_is_owned_by function v3 Message-ID: <20180220131253.GF25314@hirez.programming.kicks-ass.net> References: <20180220125829.27060-1-christian.koenig@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180220125829.27060-1-christian.koenig@amd.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 20, 2018 at 01:58:26PM +0100, Christian König wrote: > amdgpu needs to verify if userspace sends us valid addresses and the simplest > way of doing this is to check if the buffer object is locked with the ticket > of the current submission. > > Clean up the access to the ww_mutex internals by providing a function > for this and extend the check to the thread owning the underlying mutex. > Signed-off-by: Christian König Much thanks for Cc'ing the relevant maintainers :/ > --- > include/linux/ww_mutex.h | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h > index 39fda195bf78..14e4149d3d9d 100644 > --- a/include/linux/ww_mutex.h > +++ b/include/linux/ww_mutex.h > @@ -358,4 +358,21 @@ static inline bool ww_mutex_is_locked(struct ww_mutex *lock) > return mutex_is_locked(&lock->base); > } > > +/** > + * ww_mutex_is_owned_by - is the w/w mutex locked by this task in that context > + * @lock: the mutex to be queried > + * @ctx: the w/w acquire context to test > + * > + * If @ctx is not NULL test if the mutex is owned by this context. > + * If @ctx is NULL test if the mutex is owned by the current thread. > + */ > +static inline bool ww_mutex_is_owned_by(struct ww_mutex *lock, > + struct ww_acquire_ctx *ctx) > +{ > + if (ctx) > + return likely(READ_ONCE(lock->ctx) == ctx); > + else > + return likely(__mutex_owner(&lock->base) == current); > +} Much better than the previous version. If you want to bike-shed, you can leave out the 'else' and unindent the last line. I do worry about potential users of .ctx = NULL, though. It makes it far too easy to do recursive locking, which is something we should strongly discourage.