From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753264AbeBTQaW (ORCPT ); Tue, 20 Feb 2018 11:30:22 -0500 Received: from mail-wr0-f193.google.com ([209.85.128.193]:46502 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753064AbeBTQaU (ORCPT ); Tue, 20 Feb 2018 11:30:20 -0500 X-Google-Smtp-Source: AH8x225BPYFA8Mni5rMoNDEXbXsNmvIApk08JsYqW8+OrpTxh+Oyt8PZQ+Wp10lcVh/h7A+b7+cmug== Date: Tue, 20 Feb 2018 17:30:16 +0100 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: peterz@infradead.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] locking/ww_mutex: add ww_mutex_is_owned_by function v4 Message-ID: <20180220163016.GZ22199@phenom.ffwll.local> Mail-Followup-To: Christian =?iso-8859-1?Q?K=F6nig?= , peterz@infradead.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20180220144946.2510-1-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: <20180220144946.2510-1-christian.koenig@amd.com> X-Operating-System: Linux phenom 4.14.0-3-amd64 User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 20, 2018 at 03:49:46PM +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. > > v2: split amdgpu changes into separate patch as suggested by Alex > v3: change logic as suggested by Daniel > v4: fix test in case ctx is NULL > > Signed-off-by: Christian König > --- > include/linux/ww_mutex.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h > index 39fda195bf78..fea4acc0bcbc 100644 > --- a/include/linux/ww_mutex.h > +++ b/include/linux/ww_mutex.h > @@ -358,4 +358,23 @@ 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 and not > + * locked in any context. Ok I think with the increased guarantees this needs a better kerneldoc, I think we need to at least add ".... and not locked in any context, i.e. acquired using either ww_mutex_trylock() or ww_mutex_lock() without supplying a &ww_acquire_ctx." I think with that we have a nice 1:1 mapping between the context you supply to the ww_mutex_lock function and to this one. That means generic code which takes a ctx (but can handle NULL) should dtrt no matter what. With the kerneldoc augmented: Reviewed-by: Daniel Vetter I'll probably regret this r-b too, but hey to err is human :-) Cheers, Daniel > + */ > +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); > + > + return likely(__mutex_owner(&lock->base) == current) && > + likely(READ_ONCE(lock->ctx) == NULL; > +} > + > #endif > -- > 2.14.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch