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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8AC0CA1004 for ; Tue, 5 Sep 2023 16:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243346AbjIEQtU (ORCPT ); Tue, 5 Sep 2023 12:49:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44588 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353632AbjIEG7B (ORCPT ); Tue, 5 Sep 2023 02:59:01 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15BD0CC2 for ; Mon, 4 Sep 2023 23:58:58 -0700 (PDT) Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (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 madras.collabora.co.uk (Postfix) with ESMTPSA id 268F96607186; Tue, 5 Sep 2023 07:58:56 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1693897136; bh=venc7lpeLicqLmE2B/gZSt0pO4Av75I9gxi7Zr/jLJs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=cis7Nqma2ewU7UBvc4iWTwax1TW5dMlpCBMG/ZkWfJYGO4Y2/3TMtcTs37JxBHSL4 9gH5y7h5sPidOwp0mf1JP5WWEmK4yUANa1aku+3YYESU8UFbh472E/fOXxshynh+UO DwBYAE5AUG0/HwPqXDDSIhMSggxMgHFSAB9HZLRLXTquN/Yn4CkOUQfgT3y46VSUbj TBD2+zfaTlVTxYn6KJvBjjp7ApWuQzwijoeOCsVm+b9FwtxEYTs/kg6iK9eZBIpfNZ 1+/Xf2mlsJky8kyugdiPHFId45Y9QJXxw3Ag28WxiDogDlUu/gT156SfjjvHG1Tdqq boFE1eKgi0ApQ== Date: Tue, 5 Sep 2023 08:58:54 +0200 From: Boris Brezillon To: Dmitry Osipenko Cc: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Christian =?UTF-8?B?S8O2bmln?= , Qiang Yu , Steven Price , Emma Anholt , Melissa Wen , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v16 12/20] drm/shmem-helper: Add and use lockless drm_gem_shmem_get_pages() Message-ID: <20230905085854.18203012@collabora.com> In-Reply-To: <20230903170736.513347-13-dmitry.osipenko@collabora.com> References: <20230903170736.513347-1-dmitry.osipenko@collabora.com> <20230903170736.513347-13-dmitry.osipenko@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 3 Sep 2023 20:07:28 +0300 Dmitry Osipenko wrote: > Add lockless drm_gem_shmem_get_pages() helper that skips taking reservation > lock if pages_use_count is non-zero, leveraging from atomicity of the > refcount_t. Make drm_gem_shmem_mmap() to utilize the new helper. > > Suggested-by: Boris Brezillon > Signed-off-by: Dmitry Osipenko Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index a0faef3e762d..d93ebfef20c7 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -227,6 +227,20 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem) > } > EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked); > > +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem) > +{ > + int ret; > + > + if (refcount_inc_not_zero(&shmem->pages_use_count)) > + return 0; > + > + dma_resv_lock(shmem->base.resv, NULL); > + ret = drm_gem_shmem_get_pages_locked(shmem); > + dma_resv_unlock(shmem->base.resv); > + > + return ret; > +} > + > static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem) > { > int ret; > @@ -610,10 +624,7 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct > return ret; > } > > - dma_resv_lock(shmem->base.resv, NULL); > - ret = drm_gem_shmem_get_pages_locked(shmem); > - dma_resv_unlock(shmem->base.resv); > - > + ret = drm_gem_shmem_get_pages(shmem); > if (ret) > return ret; >