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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B706C3A5A6 for ; Thu, 19 Sep 2019 15:04:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E8DE21907 for ; Thu, 19 Sep 2019 15:04:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=poorly.run header.i=@poorly.run header.b="Jc+Q99J7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389695AbfISPED (ORCPT ); Thu, 19 Sep 2019 11:04:03 -0400 Received: from mail-yw1-f68.google.com ([209.85.161.68]:43871 "EHLO mail-yw1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389382AbfISPED (ORCPT ); Thu, 19 Sep 2019 11:04:03 -0400 Received: by mail-yw1-f68.google.com with SMTP id q7so1328799ywe.10 for ; Thu, 19 Sep 2019 08:04:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=poorly.run; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=y8vAVMHvzbWsdZXn87+UYmHO8hhkPrYpqOnkXz4LuK4=; b=Jc+Q99J7jDIc8UMXcQDlm6SXih7dlteWgLvH5grEUGae4NVRt4TvQIWgsD3ew8wd8H Rk0+EeCuKKC/Qe6EEteFSlaYgu7iz+WshpRtuG1Fh3erqb9ZKUyc9Zp/RHRN5qnIoKV5 HuIBSgTygqDzLgFUN0/kARz3cOk78VT6ZxrQZGbvWVg0VXXNWRizpbOya3+bZZEY2uO6 ezY2cFsaEvFpvsntH/WZ5Ep7CKukH+NjSh8eLtJ0teknFJ4ruievQWT1+llnlhmK6+FA ZOHgvvvaRGXEXUk1GAqJOskx6dzTUJCA4Nje7xulbHB8kwl3dQhhbUfEMpAlqmrGIO7s HJOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=y8vAVMHvzbWsdZXn87+UYmHO8hhkPrYpqOnkXz4LuK4=; b=Ud5IulIi1k2CxqxGHoe7bs5v/DeCxYoMvrr+igiJOdfrcNArRrkEiVCv0HlWBF5NmC VUcID2G5y/CBgLqSlsQXbECKBHjvLwGlGoyux+sv7XzEoYSzT9CPQQ86Babmj3rkrKOG GEBhlaMwIPx3V5lGF0Nh0u/1i/laaK42I7TFKk9gn41aaEY4GXnhjVf4BWy8lu5q/sSM 3Wv5JcRt8y5jL0Ag6g4U8UZ2qkSFVG1VG6upfX7yKcQiRDL/TlmiMi9sSjjsxJqj9iw/ /Pea7N/XqksfJqFbtmV5Mf9h14NCUktPX+6EHsyHOIRJHAVudy/lq4leBTv3E82+EdTU Jbew== X-Gm-Message-State: APjAAAVetK06RTUij/uVvpnhu80m6D07mZJpN1MLLGr4fkU6N5CzGwQY rWRkmE4pXefzhnNpsjm+e9KaEA== X-Google-Smtp-Source: APXvYqwx9wl4Q0hspgID6pNeOiMOJiNK3Q7E3XtH1k1AlBb6iwVW+mou23+ZcKZPPoCGDVoNKH2iBQ== X-Received: by 2002:a81:7dc5:: with SMTP id y188mr7915294ywc.69.1568905442311; Thu, 19 Sep 2019 08:04:02 -0700 (PDT) Received: from localhost ([2620:0:1013:11:89c6:2139:5435:371d]) by smtp.gmail.com with ESMTPSA id d63sm1921007ywe.55.2019.09.19.08.04.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2019 08:04:01 -0700 (PDT) Date: Thu, 19 Sep 2019 11:04:01 -0400 From: Sean Paul To: Daniel Vetter Cc: Sean Paul , dri-devel , Sean Paul , Rob Clark , Deepak Rawat , Thomas Hellstrom , Maarten Lankhorst , Maxime Ripard , David Airlie , stable Subject: Re: [PATCH] drm: damage_helper: Fix race checking plane->state->fb Message-ID: <20190919150401.GV218215@art_vandelay> References: <20190904202938.110207-1-sean@poorly.run> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Sep 05, 2019 at 12:41:27PM +0200, Daniel Vetter wrote: > On Wed, Sep 4, 2019 at 10:29 PM Sean Paul wrote: > > > > From: Sean Paul > > > > Since the dirtyfb ioctl doesn't give us any hints as to which plane is > > scanning out the fb it's marking as damaged, we need to loop through > > planes to find it. > > > > Currently we just reach into plane state and check, but that can race > > with another commit changing the fb out from under us. This patch locks > > the plane before checking the fb and will release the lock if the plane > > is not displaying the dirty fb. > > > > Fixes: b9fc5e01d1ce ("drm: Add helper to implement legacy dirtyfb") > > Cc: Rob Clark > > Cc: Deepak Rawat > > Cc: Daniel Vetter > > Cc: Thomas Hellstrom > > Cc: Maarten Lankhorst > > Cc: Maxime Ripard > > Cc: Sean Paul > > Cc: David Airlie > > Cc: Daniel Vetter > > Cc: dri-devel@lists.freedesktop.org > > Cc: # v5.0+ > > Reported-by: Daniel Vetter > > Signed-off-by: Sean Paul > > --- > > drivers/gpu/drm/drm_damage_helper.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c > > index 8230dac01a89..3a4126dc2520 100644 > > --- a/drivers/gpu/drm/drm_damage_helper.c > > +++ b/drivers/gpu/drm/drm_damage_helper.c > > @@ -212,8 +212,14 @@ int drm_atomic_helper_dirtyfb(struct drm_framebuffer *fb, > > drm_for_each_plane(plane, fb->dev) { > > struct drm_plane_state *plane_state; > > > > - if (plane->state->fb != fb) > > + ret = drm_modeset_lock(&plane->mutex, state->acquire_ctx); > > + if (ret) > > I think for paranoid safety we should have a WARN_ON(ret == -EALREADY) > here. It should be impossible, but if it's not for some oddball > reason, we'll blow up. drm_modeset_lock eats EALREADY and returns 0 for that case, so I guess it depends _how_ paranoid you want to be here :-) > > With that: Reviewed-by: Daniel Vetter > > But please give this a spin with some workloads and the ww_mutex > slowpath debugging enabled, just to makre sure. Ok, had a chance to run through some tests this morning with CONFIG_DEBUG_WW_MUTEX_SLOWPATH and things lgtm Sean > -Daniel > > > + goto out; > > + > > + if (plane->state->fb != fb) { > > + drm_modeset_unlock(&plane->mutex); > > continue; > > + } > > > > plane_state = drm_atomic_get_plane_state(state, plane); > > if (IS_ERR(plane_state)) { > > -- > > Sean Paul, Software Engineer, Google / Chromium OS > > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- Sean Paul, Software Engineer, Google / Chromium OS