From patchwork Fri Apr 8 16:13:21 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: 12806922 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 4CC38C4321E for ; Fri, 8 Apr 2022 16:13:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229944AbiDHQPz (ORCPT ); Fri, 8 Apr 2022 12:15:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229537AbiDHQPx (ORCPT ); Fri, 8 Apr 2022 12:15:53 -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 E67AF39BA4 for ; Fri, 8 Apr 2022 09:13:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649434428; 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=7QI3SswaraTV8idrWcTwBVC+GiIL0ijW6quL8YZNa3g=; b=M3A6/acuehP4pghs7lbcXYlRcrvqgcCiesf0C7wwQH53XQcCZVS6HIvSV08a9UVqsZl4yh 1u+FJVBz9bha77tD/9m6YnBUJD71BaJ9MVTuCcF8WQN/RxGPioohCSIiWn4dEqvlhfkE7d 9V0LkH6Z9BjeJ/ImIJLaf+oKHbXYS2E= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-207-jiIK7-XUNA2um1L1TktoNA-1; Fri, 08 Apr 2022 12:13:47 -0400 X-MC-Unique: jiIK7-XUNA2um1L1TktoNA-1 Received: by mail-wm1-f69.google.com with SMTP id z16-20020a05600c0a1000b0038bebbd8548so6159947wmp.3 for ; Fri, 08 Apr 2022 09:13:46 -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=7QI3SswaraTV8idrWcTwBVC+GiIL0ijW6quL8YZNa3g=; b=im14cncukq78D3rH0Vqs5NYfBmX6GfvzVNhNI1RiATNyAhR8Z+YMinWt1ssC5nEFVp cvyFdKwn6brAqgQYRStKcP0/4UbLYoc+yAz+R0FQUybta2G0JwVmkPiT+qSV3fbdXJ6w ih+oPtGE89XjuyhlDBUBV+R3wyFTT7hHsOYbhXdF7RLEJrXYVgXLcZmFrou21ZFu7uPs JcLnic6NEXAn+wPUZL5tRxCLctSxuETGaYJtalPTR9n1KqUWEbZPBYeYn6C8u52WgZOi OeIF371mMRAS0QOlAO2bieEtyG2KE+Nxt6kaX7Qos2M9fOWwnv+SxilB75qh4Yfl2OHT 6ypg== X-Gm-Message-State: AOAM533owmLzBmByFNk9vW5/N6k1n8hZioRKtBZTQyf2ZjyETEYPUlr8 d6dMHaNO3u5HXrvZcQEf0w+CuMhXS8GEo8w5aEiN5d3aqsJRKhPQWcCdc8Z4oxmrq0Gk9fjlfYX dNnpr9rEoRKGjCH/sNSqk5d0= X-Received: by 2002:adf:fa4c:0:b0:205:7cb2:e6f0 with SMTP id y12-20020adffa4c000000b002057cb2e6f0mr15284858wrr.218.1649434425686; Fri, 08 Apr 2022 09:13:45 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyYRy6iFg+nUxs9pKZmeBKF3byaeUvogbu8dmOibs9HJxOPyzETU8IRSiW1efmqzGmnYftbww== X-Received: by 2002:adf:fa4c:0:b0:205:7cb2:e6f0 with SMTP id y12-20020adffa4c000000b002057cb2e6f0mr15284837wrr.218.1649434425421; Fri, 08 Apr 2022 09:13:45 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id t15-20020adfeb8f000000b002060d26c211sm14377455wrn.114.2022.04.08.09.13.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Apr 2022 09:13:45 -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 , Guenter Roeck , Helge Deller , Sam Ravnborg , Xiyu Yang , Zhen Lei , linux-fbdev@vger.kernel.org Subject: [PATCH v2 4/5] fbdev: Fix some race conditions between fbmem and sysfb Date: Fri, 8 Apr 2022 18:13:21 +0200 Message-Id: <20220408161322.270176-5-javierm@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220408161322.270176-1-javierm@redhat.com> References: <20220408161322.270176-1-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 --- 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, 31 insertions(+), 11 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index bcdbbe543466..6cb73193410e 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 @@ -1582,22 +1583,30 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, * this lock. */ mutex_unlock(®istration_lock); - if (dev_is_platform(device)) { - platform_device_unregister(to_platform_device(device)); - } else { - /* - * If it's not a platform device, at least print a warning. A - * fix would add to code to remove the device from the system. - */ - pr_warn("fb%d: cannot remove device\n", i); - /* call unregister_framebuffer() so it can take the lock */ - unregister_framebuffer(registered_fb[i]); + 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. + */ + platform_device_unregister(to_platform_device(device)); + } else { + /* + * If it's not a platform device, at least print a warning. A + * fix would add to code to remove the device from the system. + */ + pr_warn("fb%d: cannot remove device\n", i); + /* call unregister_framebuffer() so it can take the lock */ + unregister_framebuffer(registered_fb[i]); + } } - mutex_lock(®istration_lock); /* * Restart the removal loop now that the device has been * unregistered and its associated framebuffer gone. */ + mutex_lock(®istration_lock); goto restart_removal; } } @@ -1758,6 +1767,17 @@ 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);