From patchwork Wed Apr 20 08:53:01 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: 12819950 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 8BAB7C433FE for ; Wed, 20 Apr 2022 08:53:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376992AbiDTI4N (ORCPT ); Wed, 20 Apr 2022 04:56:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376984AbiDTI4K (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 6FFD13818C for ; Wed, 20 Apr 2022 01:53:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650444804; 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=Brj5kPf1vp2+xvAmZf1o0QRVBdqqcyn2KbRWKGy9p24=; b=LKoBTEmSFbu6Hb/PWvw2HxpFZdPyIxF6zb5C0GtmJVD6hEVTYTa7/mHdvFu8O4y2fDmKMv fBDAngLp7GiJ0LjJDl0K8T+K3BwvqKZPuVrm3S4LTJCxEedjp9IWQkjJkTYgaRJ6KD4zqY 0rwOE3DhM/XI3tD8g4CzQMN26ytJ/V4= 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-121-MSxn-xiPMq2FyC5PEYjL2w-1; Wed, 20 Apr 2022 04:53:20 -0400 X-MC-Unique: MSxn-xiPMq2FyC5PEYjL2w-1 Received: by mail-wm1-f71.google.com with SMTP id 125-20020a1c0283000000b003928cd3853aso2160664wmc.9 for ; Wed, 20 Apr 2022 01:53:20 -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=Brj5kPf1vp2+xvAmZf1o0QRVBdqqcyn2KbRWKGy9p24=; b=g1EbbHnV182lm2a8rLBaRu9RWEzeKS2lkVzdTNdfFFeBezHGxlx8rgTQYbkWtOQEXJ oGRXti0AsmXUlgkFdNQ5grxD0EE1sPg31p+o0nfO7kye847+ERa3vKhtnczNQ6Jmchee uwo4SjSbL3I9RpYvKlVy3eOwGZW4qK0s3WhjD2BrVtfeADlZKJBpZB8N2eT3rLDlWb4x sE97a1ZvF6lF1Yld0r5P7z3GeKS3N152SPF7BftJr+PcGgJOj9OXaB01GnzaKfJlgJdT V+f6rAW0QaOf568g4VDnMtYSYTcRJPVaJZY8W8fmuSMc+MORFzUgCKDF26uZBo58S2ck 8SkQ== X-Gm-Message-State: AOAM5339buZE1GsKUB6O+SO04QY6or5a3iJdXKJSP8qUNXA2F7Dxpx9n IFHHgzs5L0d0T52AjSZDjIQyriF1DbhWjqnh6rH9hlMw5rsKM9yi2S8PyQZ2Xf9IqvFBYH8AafQ j2jiplsWU9iSRE6DcwxhZWDE= X-Received: by 2002:a1c:3b87:0:b0:38e:ae26:87c3 with SMTP id i129-20020a1c3b87000000b0038eae2687c3mr2579007wma.117.1650444799066; Wed, 20 Apr 2022 01:53:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzisiOp22RzVsqiZMkzUyzv5bMt9mjVky1BUXdtYfPSyZywBr9TqZ6k14/+L6ay5mbfLa1Byw== X-Received: by 2002:a1c:3b87:0:b0:38e:ae26:87c3 with SMTP id i129-20020a1c3b87000000b0038eae2687c3mr2578982wma.117.1650444798811; Wed, 20 Apr 2022 01:53:18 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id i14-20020a0560001ace00b0020aac00f862sm1895343wry.98.2022.04.20.01.53.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Apr 2022 01:53:18 -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 , Zhen Lei , linux-fbdev@vger.kernel.org Subject: [PATCH v3 3/5] fbdev: Restart conflicting fb removal loop when unregistering devices Date: Wed, 20 Apr 2022 10:53:01 +0200 Message-Id: <20220420085303.100654-4-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 Drivers that want to remove registered conflicting framebuffers prior to register their own framebuffer, calls remove_conflicting_framebuffers(). This function takes the registration_lock mutex, to prevent a races when drivers register framebuffer devices. But if a conflicting framebuffer device is found, the underlaying platform device is unregistered and this will lead to the platform driver .remove callback to be called, which in turn will call to the unregister_framebuffer() that takes the same lock. To prevent this, a struct fb_info.forced_out field was used as indication to unregister_framebuffer() whether the mutex has to be grabbed or not. A cleaner solution is to drop the lock before platform_device_unregister() so unregister_framebuffer() can take it when called from the fbdev driver, and just grab the lock again after the device has been registered and do a removal loop restart. Since the framebuffer devices will already be removed, the loop would just finish when no more conflicting framebuffers are found. Suggested-by: Daniel Vetter Signed-off-by: Javier Martinez Canillas Reviewed-by: Daniel Vetter --- (no changes since v1) drivers/video/fbdev/core/fbmem.c | 22 +++++++++++++++------- include/linux/fb.h | 1 - 2 files changed, 15 insertions(+), 8 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 84427470367b..0bb459258df3 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1553,6 +1553,7 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, { int i; +restart_removal: /* check all firmware fbs and kick off if the base addr overlaps */ for_each_registered_fb(i) { struct apertures_struct *gen_aper; @@ -1585,12 +1586,23 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, pr_warn("fb%d: no device set\n", i); do_unregister_framebuffer(registered_fb[i]); } else if (dev_is_platform(device)) { - registered_fb[i]->forced_out = true; + /* + * 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)); + 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 + * unregistered and its associated framebuffer gone. + */ + goto restart_removal; } } } @@ -1897,13 +1909,9 @@ EXPORT_SYMBOL(register_framebuffer); void unregister_framebuffer(struct fb_info *fb_info) { - bool forced_out = fb_info->forced_out; - - if (!forced_out) - mutex_lock(®istration_lock); + mutex_lock(®istration_lock); do_unregister_framebuffer(fb_info); - if (!forced_out) - mutex_unlock(®istration_lock); + mutex_unlock(®istration_lock); } EXPORT_SYMBOL(unregister_framebuffer); diff --git a/include/linux/fb.h b/include/linux/fb.h index f95da1af9ff6..b781bc721113 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -502,7 +502,6 @@ struct fb_info { } *apertures; bool skip_vt_switch; /* no VT switch on suspend/resume required */ - bool forced_out; /* set when being removed by another driver */ }; static inline struct apertures_struct *alloc_apertures(unsigned int max_num) { 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: 12819949 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 ; 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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);