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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hblny-0007pX-2X; Fri, 14 Jun 2019 12:59:42 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 80D3E2013F741; Fri, 14 Jun 2019 14:59:40 +0200 (CEST) Date: Fri, 14 Jun 2019 14:59:40 +0200 From: Peter Zijlstra To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: daniel@ffwll.ch, l.stach@pengutronix.de, linux+etnaviv@armlinux.org.uk, christian.gmeiner@gmail.com, yuq825@gmail.com, eric@anholt.net, thellstrom@vmware.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, etnaviv@lists.freedesktop.org, lima@lists.freedesktop.org Subject: Re: [PATCH 3/6] drm/gem: use new ww_mutex_(un)lock_for_each macros Message-ID: <20190614125940.GP3436@hirez.programming.kicks-ass.net> References: <20190614124125.124181-1-christian.koenig@amd.com> <20190614124125.124181-4-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: <20190614124125.124181-4-christian.koenig@amd.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 14, 2019 at 02:41:22PM +0200, Christian König wrote: > Use the provided macros instead of implementing deadlock handling on our own. > > Signed-off-by: Christian König > --- > drivers/gpu/drm/drm_gem.c | 49 ++++++++++----------------------------- > 1 file changed, 12 insertions(+), 37 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 50de138c89e0..6e4623d3bee2 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -1307,51 +1307,26 @@ int > drm_gem_lock_reservations(struct drm_gem_object **objs, int count, > struct ww_acquire_ctx *acquire_ctx) > { > - int contended = -1; > + struct ww_mutex *contended; > int i, ret; > > ww_acquire_init(acquire_ctx, &reservation_ww_class); > > -retry: > - if (contended != -1) { > - struct drm_gem_object *obj = objs[contended]; > - > - ret = ww_mutex_lock_slow_interruptible(&obj->resv->lock, > - acquire_ctx); > - if (ret) { > - ww_acquire_done(acquire_ctx); > - return ret; > - } > - } > - > - for (i = 0; i < count; i++) { > - if (i == contended) > - continue; > - > - ret = ww_mutex_lock_interruptible(&objs[i]->resv->lock, > - acquire_ctx); > - if (ret) { > - int j; > - > - for (j = 0; j < i; j++) > - ww_mutex_unlock(&objs[j]->resv->lock); > - > - if (contended != -1 && contended >= i) > - ww_mutex_unlock(&objs[contended]->resv->lock); > - > - if (ret == -EDEADLK) { > - contended = i; > - goto retry; retry here, starts the whole locking loop. > - } > - > - ww_acquire_done(acquire_ctx); > - return ret; > - } > - } +#define ww_mutex_unlock_for_each(loop, pos, contended) \ + if (!IS_ERR(contended)) { \ + if (contended) \ + ww_mutex_unlock(contended); \ + contended = (pos); \ + loop { \ + if (contended == (pos)) \ + break; \ + ww_mutex_unlock(pos); \ + } \ + } + +#define ww_mutex_lock_for_each(loop, pos, contended, ret, intr, ctx) \ + for (contended = ERR_PTR(-ENOENT); ({ \ + __label__ relock, next; \ + ret = -ENOENT; \ + if (contended == ERR_PTR(-ENOENT)) \ + contended = NULL; \ + else if (contended == ERR_PTR(-EDEADLK)) \ + contended = (pos); \ + else \ + goto next; \ + loop { \ + if (contended == (pos)) { \ + contended = NULL; \ + continue; \ + } \ +relock: \ + ret = !(intr) ? ww_mutex_lock(pos, ctx) : \ + ww_mutex_lock_interruptible(pos, ctx); \ + if (ret == -EDEADLK) { \ + ww_mutex_unlock_for_each(loop, pos, \ + contended); \ + contended = ERR_PTR(-EDEADLK); \ + goto relock; \ while relock here continues where it left of and doesn't restart @loop. Or am I reading this monstrosity the wrong way? + } \ + break; \ +next: \ + continue; \ + } \ + }), ret != -ENOENT;) + > + ww_mutex_lock_for_each(for (i = 0; i < count; i++), > + &objs[i]->resv->lock, contended, ret, true, > + acquire_ctx) > + if (ret) > + goto error; > > ww_acquire_done(acquire_ctx); > > return 0; > + > +error: > + ww_mutex_unlock_for_each(for (i = 0; i < count; i++), > + &objs[i]->resv->lock, contended); > + ww_acquire_done(acquire_ctx); > + return ret; > } > EXPORT_SYMBOL(drm_gem_lock_reservations);