From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932070AbcFVXKy (ORCPT ); Wed, 22 Jun 2016 19:10:54 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46398 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751721AbcFVWl6 (ORCPT ); Wed, 22 Jun 2016 18:41:58 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Hellstrom , David Herrmann , Daniel Vetter , Tvrtko Ursulin , Hans de Goede Subject: [PATCH 4.4 65/75] drm/core: Do not preserve framebuffer on rmfb, v4. Date: Wed, 22 Jun 2016 15:41:27 -0700 Message-Id: <20160622223503.257368331@linuxfoundation.org> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160622223500.055133765@linuxfoundation.org> References: <20160622223500.055133765@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Maarten Lankhorst commit f2d580b9a8149735cbc4b59c4a8df60173658140 upstream. It turns out that preserving framebuffers after the rmfb call breaks vmwgfx userspace. This was originally introduced because it was thought nobody relied on the behavior, but unfortunately it seems there are exceptions. drm_framebuffer_remove may fail with -EINTR now, so a straight revert is impossible. There is no way to remove the framebuffer from the lists and active planes without introducing a race because of the different locking requirements. Instead call drm_framebuffer_remove from a workqueue, which is unaffected by signals. Changes since v1: - Add comment. Changes since v2: - Add fastpath for refcount = 1. (danvet) Changes since v3: - Rebased. - Restore lastclose framebuffer removal too. Fixes: 13803132818c ("drm/core: Preserve the framebuffer after removing it.") Testcase: kms_rmfb_basic References: https://lists.freedesktop.org/archives/dri-devel/2016-March/102876.html Cc: Thomas Hellstrom Cc: David Herrmann Reviewed-by: Daniel Vetter Tested-by: Thomas Hellstrom #v3 Tested-by: Tvrtko Ursulin Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/6c63ca37-0e7e-ac7f-a6d2-c7822e3d611f@linux.intel.com Signed-off-by: Hans de Goede Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_crtc.c | 60 +++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 55 insertions(+), 5 deletions(-) --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -3316,6 +3316,24 @@ int drm_mode_addfb2(struct drm_device *d return 0; } +struct drm_mode_rmfb_work { + struct work_struct work; + struct list_head fbs; +}; + +static void drm_mode_rmfb_work_fn(struct work_struct *w) +{ + struct drm_mode_rmfb_work *arg = container_of(w, typeof(*arg), work); + + while (!list_empty(&arg->fbs)) { + struct drm_framebuffer *fb = + list_first_entry(&arg->fbs, typeof(*fb), filp_head); + + list_del_init(&fb->filp_head); + drm_framebuffer_remove(fb); + } +} + /** * drm_mode_rmfb - remove an FB from the configuration * @dev: drm device for the ioctl @@ -3356,7 +3374,25 @@ int drm_mode_rmfb(struct drm_device *dev mutex_unlock(&dev->mode_config.fb_lock); mutex_unlock(&file_priv->fbs_lock); - drm_framebuffer_unreference(fb); + /* + * we now own the reference that was stored in the fbs list + * + * drm_framebuffer_remove may fail with -EINTR on pending signals, + * so run this in a separate stack as there's no way to correctly + * handle this after the fb is already removed from the lookup table. + */ + if (atomic_read(&fb->refcount.refcount) > 1) { + struct drm_mode_rmfb_work arg; + + INIT_WORK_ONSTACK(&arg.work, drm_mode_rmfb_work_fn); + INIT_LIST_HEAD(&arg.fbs); + list_add_tail(&fb->filp_head, &arg.fbs); + + schedule_work(&arg.work); + flush_work(&arg.work); + destroy_work_on_stack(&arg.work); + } else + drm_framebuffer_unreference(fb); return 0; @@ -3509,7 +3545,6 @@ out_err1: return ret; } - /** * drm_fb_release - remove and free the FBs on this file * @priv: drm file for the ioctl @@ -3524,6 +3559,9 @@ out_err1: void drm_fb_release(struct drm_file *priv) { struct drm_framebuffer *fb, *tfb; + struct drm_mode_rmfb_work arg; + + INIT_LIST_HEAD(&arg.fbs); /* * When the file gets released that means no one else can access the fb @@ -3536,10 +3574,22 @@ void drm_fb_release(struct drm_file *pri * at it any more. */ list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) { - list_del_init(&fb->filp_head); + if (atomic_read(&fb->refcount.refcount) > 1) { + list_move_tail(&fb->filp_head, &arg.fbs); + } else { + list_del_init(&fb->filp_head); - /* This drops the fpriv->fbs reference. */ - drm_framebuffer_unreference(fb); + /* This drops the fpriv->fbs reference. */ + drm_framebuffer_unreference(fb); + } + } + + if (!list_empty(&arg.fbs)) { + INIT_WORK_ONSTACK(&arg.work, drm_mode_rmfb_work_fn); + + schedule_work(&arg.work); + flush_work(&arg.work); + destroy_work_on_stack(&arg.work); } }