From patchwork Wed Apr 20 08:53:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Javier Martinez Canillas X-Patchwork-Id: 564128 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 3DC91C433F5 for ; Wed, 20 Apr 2022 08:53:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376995AbiDTI4L (ORCPT ); Wed, 20 Apr 2022 04:56:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376987AbiDTI4K (ORCPT ); Wed, 20 Apr 2022 04:56:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 998D63B3CA for ; Wed, 20 Apr 2022 01:53:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650444803; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9ipOD+iHYz0MO8ka3xCh5rdeCaG6XqtVDndckQG+34g=; b=bcHujS5QuQfaFjSDWP4KwrBo/levikDShumZmmEqLx4Tn/LV4AuPL5M1Muu/IGBD5WwQo6 PpxSWZfiAOn3dt8wIyDk5Krw23HOiDQZLa0/TUggnXO7lOWYSEgz4fGP/eJSkJtcgwJ1J+ 9m21eU6EH4alw9HF9zDyT/7bBVJesdw= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-473-szDkQ2J2P_mWw6e3g-3TDQ-1; Wed, 20 Apr 2022 04:53:22 -0400 X-MC-Unique: szDkQ2J2P_mWw6e3g-3TDQ-1 Received: by mail-wr1-f72.google.com with SMTP id e2-20020adfa442000000b0020a91fa37b9so192629wra.10 for ; Wed, 20 Apr 2022 01:53:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=9ipOD+iHYz0MO8ka3xCh5rdeCaG6XqtVDndckQG+34g=; b=1Hd0Ta4686PZF47+gGaVW3BirVXBqk0mw/kbfKIbJ0rf9kq4lipB6PUML58kTMdDaL tVH8ND1fNqSdciYgdlnJXslVE6gBS3Uz30JS0goRl6v1tjMf7XRd1D+aH2hQAgZMBuCp up+1iyhZqQbCTxKOcoW7XjNB4SlhIzDwHRc9o34ggOExseALFZWHzVaTCe6MtROlSgG4 6eq7HW4Ap7sGGMyAS1QqoOgcZKjzQnQ/3bZuQHVa3Zk7FlfvlZahCc4u+Vsxr8mW+ykJ dVInko0qlmLcZJuDV6qGC7p69a4g61aX8RTQ6fO4/D7Iwf63sdugQyJ2MupCn3OoqYID embA== X-Gm-Message-State: AOAM531XSqu8mefWIKmOtEqGGoZqASx8obTzuJsheKIhXL/vPQReMVXE R39z8Pf9InP0rRpi6q9gmbs9Q1+j4NySe8lkKmbRdCdN05RNeFm7XESUdLOCY+Y3umlp7SPTpjt J3dMaiK9zc8DoriUJuXhYEkc= X-Received: by 2002:a5d:5392:0:b0:207:aaca:9bd8 with SMTP id d18-20020a5d5392000000b00207aaca9bd8mr14859668wrv.615.1650444800320; Wed, 20 Apr 2022 01:53:20 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyZbvPSUyZXNVpsoDxEqgIOir/+9fpJtKe5GQ7jt7d1nsakg7f78pMNvQTiKbTLOPgE1YW8kA== X-Received: by 2002:a5d:5392:0:b0:207:aaca:9bd8 with SMTP id d18-20020a5d5392000000b00207aaca9bd8mr14859645wrv.615.1650444800067; Wed, 20 Apr 2022 01:53:20 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id i14-20020a0560001ace00b0020aac00f862sm1895343wry.98.2022.04.20.01.53.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Apr 2022 01:53:19 -0700 (PDT) From: Javier Martinez Canillas To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , Daniel Vetter , dri-devel@lists.freedesktop.org, Thomas Zimmermann , Javier Martinez Canillas , Alex Deucher , Changcheng Deng , Daniel Vetter , Helge Deller , Sam Ravnborg , Tetsuo Handa , Yizhuo Zhai , Zhen Lei , linux-fbdev@vger.kernel.org Subject: [PATCH v3 4/5] fbdev: Fix some race conditions between fbmem and sysfb Date: Wed, 20 Apr 2022 10:53:02 +0200 Message-Id: <20220420085303.100654-5-javierm@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220420085303.100654-1-javierm@redhat.com> References: <20220420085303.100654-1-javierm@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org The platform devices registered in sysfb match with a firmware-based fbdev or DRM driver, that are used to have early graphics using framebuffers set up by the system firmware. Real DRM drivers later are probed and remove all conflicting framebuffers, leading to these platform devices for generic drivers to be unregistered. But the current solution has two issues that this patch fixes: 1) It is a layering violation for the fbdev core to unregister a device that was registered by sysfb. Instead, the sysfb_try_unregister() helper function can be called for sysfb to attempt unregistering the device if is the one registered. 2) The sysfb_init() function could be called after a DRM driver is probed and requested to unregister devices for drivers with a conflicting fb. To prevent this, disable any future sysfb platform device registration by calling sysfb_disable(), if a driver requested to remove conflicting framebuffers with remove_conflicting_framebuffers(). There are video drivers (e.g: vga16fb) that register their own device and don't use the sysfb infrastructure for that, so an unregistration has to be forced by fbmem if sysfb_try_unregister() fails to do the unregister. Suggested-by: Daniel Vetter Signed-off-by: Javier Martinez Canillas Reviewed-by: Daniel Vetter --- (no changes since v2) Changes in v2: - Explain in the commit message that fbmem has to unregister the device as fallback if a driver registered the device itself (Daniel Vetter). - Also explain that fallback in a comment in the code (Daniel Vetter). - Don't encode in fbmem the assumption that sysfb will always register platform devices (Daniel Vetter). - Add a FIXME comment about drivers registering devices (Daniel Vetter). drivers/video/fbdev/core/fbmem.c | 42 ++++++++++++++++++++++++++++---- 1 file changed, 37 insertions(+), 5 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 0bb459258df3..8098305879f8 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -1585,18 +1586,38 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, if (!device) { pr_warn("fb%d: no device set\n", i); do_unregister_framebuffer(registered_fb[i]); - } else if (dev_is_platform(device)) { + } else { /* * Drop the lock because if the device is unregistered, its * driver will call to unregister_framebuffer(), that takes * this lock. */ mutex_unlock(®istration_lock); - platform_device_unregister(to_platform_device(device)); + /* + * First attempt the device to be unregistered by sysfb. + */ + if (!sysfb_try_unregister(device)) { + if (dev_is_platform(device)) { + /* + * FIXME: sysfb didn't register this device, is a platform + * device registered by a video driver (e.g: vga16fb), so + * force its unregistration here. A proper fix would be to + * move all device registration to the sysfb infrastructure + * or platform code. + */ + platform_device_unregister(to_platform_device(device)); + } else { + /* + * If is not a platform device, at least print a warning. A + * fix would add to make the code that registered the device + * to also unregister it. + */ + pr_warn("fb%d: cannot remove device\n", i); + /* call unregister_framebuffer() since the lock was dropped */ + unregister_framebuffer(registered_fb[i]); + } + } mutex_lock(®istration_lock); - } else { - pr_warn("fb%d: cannot remove device\n", i); - do_unregister_framebuffer(registered_fb[i]); } /* * Restart the removal loop now that the device has been @@ -1762,6 +1783,17 @@ int remove_conflicting_framebuffers(struct apertures_struct *a, do_free = true; } + /* + * If a driver asked to unregister a platform device registered by + * sysfb, then can be assumed that this is a driver for a display + * that is set up by the system firmware and has a generic driver. + * + * Drivers for devices that don't have a generic driver will never + * ask for this, so let's assume that a real driver for the display + * was already probed and prevent sysfb to register devices later. + */ + sysfb_disable(); + mutex_lock(®istration_lock); do_remove_conflicting_framebuffers(a, name, primary); mutex_unlock(®istration_lock);