From 371ba0126a39b147347a44140589f1d04ed8f845 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Mon, 22 May 2017 15:59:45 +0200 Subject: [PATCH] drm: Fix deadlock retry loop in page_flip_ioctl MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit I failed to properly onion-wrap the unwind code: We acquire the vblank reference before we start with the wait-wound locking dance, hence we must make sure we retry before we drop the reference. Oops. v2: The vblank_put must be after the frambuffer_put (Michel). I suck at unwrapping code that doesn't use separate labels for each stage, but checks each pointer first ... While re-reading everything I also realized that we must clean up the fb refcounts, and specifically plane->old_fb before we drop the locks, either in the final unlocking, or in the w/w retry path. Hence the correct fix is to drop the vblank_put to the very bottom. Fixes: 52db7695ef4d ("drm: Roll out acquire context for the page_flip ioctl") Cc: Harry Wentland Cc: Daniel Vetter Cc: Jani Nikula Cc: Sean Paul Cc: David Airlie Cc: dri-devel@lists.freedesktop.org Reported-by: Tommi Rantala Cc: Tommi Rantala Cc: Michel Dänzer Tested-by: Tommi Rantala Reviewed-by: Michel Dänzer Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20170522135945.28831-1-daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_plane.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index fedd4d60d9cd5..5dc8c4350602a 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -948,8 +948,6 @@ retry: } out: - if (ret && crtc->funcs->page_flip_target) - drm_crtc_vblank_put(crtc); if (fb) drm_framebuffer_put(fb); if (crtc->primary->old_fb) @@ -964,5 +962,8 @@ out: drm_modeset_drop_locks(&ctx); drm_modeset_acquire_fini(&ctx); + if (ret && crtc->funcs->page_flip_target) + drm_crtc_vblank_put(crtc); + return ret; } -- 2.39.5