From patchwork Wed Apr 6 16:06:31 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: 558387 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 65416C433F5 for ; Wed, 6 Apr 2022 17:55:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239553AbiDFR5P (ORCPT ); Wed, 6 Apr 2022 13:57:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32934 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239566AbiDFR5J (ORCPT ); Wed, 6 Apr 2022 13:57:09 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1A0971A771B for ; Wed, 6 Apr 2022 09:06:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649261211; 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=env1f3IYLBLUN0bDvO5fF8B61UkIhGpjGygidOmSM6sNxq2RRqUQk+b68iXXTSj+PrM2/k 2MtvZZsFpN9JPSFJ1ntmxscdtgciLV6J5p6g7Yrv/z+9R/fDWeJuxc1hQKjCEvvhkRmNRn H5eZjl4EoDk/wgCQafJPX5DP5sAAZ5k= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-612-fipE_XY0MkWp6ed6_Si83w-1; Wed, 06 Apr 2022 12:06:50 -0400 X-MC-Unique: fipE_XY0MkWp6ed6_Si83w-1 Received: by mail-wm1-f70.google.com with SMTP id r19-20020a7bc093000000b0038e706da7c0so1524911wmh.1 for ; Wed, 06 Apr 2022 09:06:49 -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=ZesgGlaj+PspL/qyAVGSWKoO35pXa+QGrMlNz0V4/TK9th0/6MfRN6sQUgJlztF2Hs fNiHkYQXtAWhOXyRAquE6Cv4Jo4NJwR5HHPYsOLgNrajZjs8ab4MTLKCjghppJvUXvXT ROPg8c8dKxPgMS+jLE5Hhbl/X24Qxo2Fc9F4cboX2nJsj4xEive1T8EnG5NsYU/7EmHW 5OEOpkNlYYcu3Ru91NJPALx1/HZ2LxvXcmOdwAUmGLRnri/uaHrgMFhFJ6ox7Yf9eyKp i+Bb8wgNzLBLTU03REQplbcFc1LIOt5C2BFcZwmOAwKaEuoKHPGzOc0Yd+m8Fd/Edu7r Fh/A== X-Gm-Message-State: AOAM531yDGMy9Igs/rfzgRDXM0ldn/rNsRXsDrh0k65ccuEwr03IKsqE Ycwa8e+xbHyO7NhrKFQWtlSh615fjCDqlmpOK/1rcbynkdNaxlATGnKjc9tfo6kW6Ce7gUEtdwz Snj5kf4+An4LIFUGtYWPYyF4= X-Received: by 2002:a05:600c:3b26:b0:38c:8358:4b84 with SMTP id m38-20020a05600c3b2600b0038c83584b84mr8262625wms.185.1649261208659; Wed, 06 Apr 2022 09:06:48 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwrWRPcdVNxxa0OQoFxVtMgEvN6P53Xni3VcPZinWUwk/8XrPqG2DL56DBxegaE9MICKK7T2Q== X-Received: by 2002:a05:600c:3b26:b0:38c:8358:4b84 with SMTP id m38-20020a05600c3b2600b0038c83584b84mr8262596wms.185.1649261208370; Wed, 06 Apr 2022 09:06:48 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id f1-20020a1c6a01000000b0038c9f6a3634sm5038899wmc.7.2022.04.06.09.06.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Apr 2022 09:06:48 -0700 (PDT) From: Javier Martinez Canillas To: linux-kernel@vger.kernel.org Cc: Thomas Zimmermann , Daniel Vetter , Javier Martinez Canillas , Alex Deucher , Hans de Goede , Helge Deller , Sam Ravnborg , Xiyu Yang , Zhen Lei , Zheyu Ma , dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org Subject: [RFC PATCH 4/5] fbdev: Fix some race conditions between fbmem and sysfb Date: Wed, 6 Apr 2022 18:06:31 +0200 Message-Id: <20220406160632.496684-5-javierm@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220406160632.496684-1-javierm@redhat.com> References: <20220406160632.496684-1-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 --- 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);