From patchwork Wed Apr 6 21:39:18 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: 12804133 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 66C57C4332F for ; Wed, 6 Apr 2022 21:49:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236461AbiDFVvh (ORCPT ); Wed, 6 Apr 2022 17:51:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236368AbiDFVvL (ORCPT ); Wed, 6 Apr 2022 17:51:11 -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 AB7C0657AF for ; Wed, 6 Apr 2022 14:40:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649281257; 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=U2QzSBkwn7Yafa/16sbGGbBUM4FbySeU5GGeHJm/Jx0=; b=eijo4Y+s7R0Z3IGqxaQ/vf61sKD2t8ISx5f3/2lxe8bel826T1dBDmxaV5lDiGfGXtJgdJ 2cvURDpmc8cqmBOwm5x0oepupf26b0aSKbZJITF3hhjNvYI7z/KnUuKAnDUryPB+uE+8uJ IRg6Ahvb2x3RKzPqcNvrpi+kbPqbcxQ= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-651-8kvxkqqkPBKn-q7e-3Oe8w-1; Wed, 06 Apr 2022 17:40:56 -0400 X-MC-Unique: 8kvxkqqkPBKn-q7e-3Oe8w-1 Received: by mail-wm1-f71.google.com with SMTP id i6-20020a05600c354600b0038be262d9d9so3531675wmq.8 for ; Wed, 06 Apr 2022 14:40:56 -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=U2QzSBkwn7Yafa/16sbGGbBUM4FbySeU5GGeHJm/Jx0=; b=X6mp5ko+PJLYozbfg7Z2YWJzfieS0WREp7BTosl+6BXeHLAbxKJ+Ejp6ze0q1ro2og dVuOHjtw6RbC6MPHT7Hs1wbwuv4Z+9dyS0HMV7TBYwN727iDFjB47Is1doWTH0P8J9wI xyA3u3Esh3/H+CPozvi9SGXMAQ6FSDwctK6eVacdI24kiJd7Y/t0i/UQjaPDJ74nZBCL L3bRFoL4PYIUcGGzzlafb0bVmW5LrAQypwnSF7SkepQsq2WStZZ5K3A/Mq0qVGiL8N3W uVoQYsBVUImCznGedTJyS3klqvHILqGJ8V+HorMzHs4hwvGDxYwwuyrB7rJ/yzomkgRq OdmQ== X-Gm-Message-State: AOAM532AoJSDutUrVpdZNbiCV1uVArdxgcxQugAETCniTj3LMjT2G70B MyoGpdbvE3PioRefvdkd/coP9Tzm+f48wqAZS4oAI0t+WrX+0xE2h0t5LCv0urpoO8swNa27Q6d ynnkysn8XCeWgx453k35aEG8= X-Received: by 2002:a05:600c:6004:b0:38c:6c00:4316 with SMTP id az4-20020a05600c600400b0038c6c004316mr9499666wmb.6.1649281255705; Wed, 06 Apr 2022 14:40:55 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy98rnXAztsyk4KBqYgyk86f1BpoiJOrcBFIcbWPB9DOuUKh2YKVe/1UDGOsUjrhGSlhCdgYw== X-Received: by 2002:a05:600c:6004:b0:38c:6c00:4316 with SMTP id az4-20020a05600c600400b0038c6c004316mr9499656wmb.6.1649281255447; Wed, 06 Apr 2022 14:40:55 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id o29-20020a05600c511d00b0038e3532b23csm5876020wms.15.2022.04.06.14.40.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Apr 2022 14:40:55 -0700 (PDT) From: Javier Martinez Canillas To: linux-kernel@vger.kernel.org Cc: dri-devel@lists.freedesktop.org, Thomas Zimmermann , Daniel Vetter , Javier Martinez Canillas , Alex Deucher , Guenter Roeck , Helge Deller , Sam Ravnborg , Xiyu Yang , Zhen Lei , linux-fbdev@vger.kernel.org Subject: [RESEND RFC PATCH 4/5] fbdev: Fix some race conditions between fbmem and sysfb Date: Wed, 6 Apr 2022 23:39:18 +0200 Message-Id: <20220406213919.600294-5-javierm@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220406213919.600294-1-javierm@redhat.com> References: <20220406213919.600294-1-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(). Suggested-by: Daniel Vetter Signed-off-by: Javier Martinez Canillas Reviewed-by: Daniel Vetter --- drivers/video/fbdev/core/fbmem.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index c1bfb8df9cba..acf641b05d11 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 @@ -1588,7 +1589,10 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, * unregister_framebuffer() function that takes it. */ mutex_unlock(®istration_lock); - platform_device_unregister(to_platform_device(device)); + if (!sysfb_try_unregister(device)) { + /* sysfb didn't register this device, unregister it */ + platform_device_unregister(to_platform_device(device)); + } mutex_lock(®istration_lock); /* * Restart the removal now that the platform device @@ -1781,6 +1785,17 @@ 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);