From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 33CE0C4345F for ; Wed, 24 Apr 2024 07:04:36 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7FFAC112569; Wed, 24 Apr 2024 07:04:35 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=collabora.com header.i=@collabora.com header.b="JDXd0AkD"; dkim-atps=neutral Received: from madrid.collaboradmins.com (madrid.collaboradmins.com [46.235.227.194]) by gabe.freedesktop.org (Postfix) with ESMTPS id D430E10FDAA; Wed, 24 Apr 2024 07:04:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1713942272; bh=nJVKTHFvXTmcgK94/e0JrZRbtF6RLuWFoyU5TaTbIOw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=JDXd0AkDQ8uya67kE3ZEEZf2wWXQRYf3Hz75PsC7+NlvLgkn1NHD+ydLruToXEkSZ 0ETIuuGd33BQ3FKDRAmYj30rOV6Zzsm9LiPqTLaJppVDkYkKiv1d1T5cYrHytjamZM eOKf8WpDo+YbKUcQzl+GLdftGAklXTvsk9D9Sp5xqQ5QrYyhupoISuBbBY05J9YR8M nQROEkUSxZvYCEvQxIIEQ0il0EY8Ga6rU9Mt0VbIOv6pZ+pVOszvqTYzatt7fMGo3S RXHeif6d9ORwnABYkV+QzXebbfQubxOeZYNWQiz7TXTKrIUABcDvQfoOOsCkC8XlI4 dy6KOnttCY2ZQ== Received: from localhost (cola.collaboradmins.com [195.201.22.229]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madrid.collaboradmins.com (Postfix) with ESMTPSA id 64FA63781182; Wed, 24 Apr 2024 07:04:31 +0000 (UTC) Date: Wed, 24 Apr 2024 09:04:29 +0200 From: Boris Brezillon To: =?UTF-8?B?QWRyacOhbg==?= Larumbe Cc: Qiang Yu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Rob Herring , Steven Price , Sumit Semwal , Christian =?UTF-8?B?S8O2bmln?= , Dmitry Osipenko , Zack Rusin , kernel@collabora.com, dri-devel@lists.freedesktop.org, lima@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH v2] drm/panfrost: Fix dma_resv deadlock at drm object pin time Message-ID: <20240424090429.57de7d1c@collabora.com> In-Reply-To: <20240423224651.138163-1-adrian.larumbe@collabora.com> References: <20240423224651.138163-1-adrian.larumbe@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, 23 Apr 2024 23:46:23 +0100 Adri=C3=A1n Larumbe wrote: > When Panfrost must pin an object that is being prepared a dma-buf > attachment for on behalf of another driver, the core drm gem object pinni= ng > code already takes a lock on the object's dma reservation. >=20 > However, Panfrost GEM object's pinning callback would eventually try taki= ng > the lock on the same dma reservation when delegating pinning of the object > onto the shmem subsystem, which led to a deadlock. >=20 > This can be shown by enabling CONFIG_DEBUG_WW_MUTEX_SLOWPATH, which throws > the following recursive locking situation: >=20 > weston/3440 is trying to acquire lock: > ffff000000e235a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: drm_gem_sh= mem_pin+0x34/0xb8 [drm_shmem_helper] > but task is already holding lock: > ffff000000e235a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: drm_gem_pi= n+0x2c/0x80 [drm] >=20 > Fix it by assuming the object's reservation had already been locked by the > time we reach panfrost_gem_pin. >=20 > Do the same thing for the Lima driver, as it most likely suffers from the > same issue. >=20 > Cc: Thomas Zimmermann > Cc: Dmitry Osipenko > Cc: Boris Brezillon > Cc: Steven Price > Fixes: a78027847226 ("drm/gem: Acquire reservation lock in drm_gem_{pin/u= npin}()") > Reviewed-by: Boris Brezillon > Signed-off-by: Adri=C3=A1n Larumbe > --- > drivers/gpu/drm/lima/lima_gem.c | 9 +++++++-- > drivers/gpu/drm/panfrost/panfrost_gem.c | 8 +++++++- > 2 files changed, 14 insertions(+), 3 deletions(-) >=20 > diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_= gem.c > index 7ea244d876ca..8a5bcf498ef6 100644 > --- a/drivers/gpu/drm/lima/lima_gem.c > +++ b/drivers/gpu/drm/lima/lima_gem.c > @@ -184,8 +184,13 @@ static int lima_gem_pin(struct drm_gem_object *obj) > =20 > if (bo->heap_size) > return -EINVAL; > - > - return drm_gem_shmem_pin(&bo->base); > + /* > + * Pinning can only happen in response to a prime attachment request > + * from another driver, but dma reservation locking is already being > + * handled by drm_gem_pin This comment looks a bit weird now that you call a function that doesn't have the _locked suffix. I'd be tempted to drop it, or clarify the fact drm_gem_shmem_object_pin() expects the resv lock to be held. > + */ > + drm_WARN_ON(obj->dev, obj->import_attach); Should this be moved to drm_gem_shmem_[un]pin_locked() instead of being duplicated in all overloads of ->[un]pin()? > + return drm_gem_shmem_object_pin(obj); > } > =20 > static int lima_gem_vmap(struct drm_gem_object *obj, struct iosys_map *m= ap) > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/pa= nfrost/panfrost_gem.c > index d47b40b82b0b..e3fbcb020617 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_gem.c > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c > @@ -192,7 +192,13 @@ static int panfrost_gem_pin(struct drm_gem_object *o= bj) > if (bo->is_heap) > return -EINVAL; > =20 > - return drm_gem_shmem_pin(&bo->base); > + /* > + * Pinning can only happen in response to a prime attachment request > + * from another driver, but dma reservation locking is already being > + * handled by drm_gem_pin > + */ > + drm_WARN_ON(obj->dev, obj->import_attach); > + return drm_gem_shmem_object_pin(obj); > } > =20 > static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_obj= ect *obj)