From patchwork Fri Apr 8 16:13:20 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: 558992 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 D03ADC433FE for ; Fri, 8 Apr 2022 16:13:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231460AbiDHQPz (ORCPT ); Fri, 8 Apr 2022 12:15:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229944AbiDHQPv (ORCPT ); Fri, 8 Apr 2022 12:15:51 -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 75CE9ECB35 for ; Fri, 8 Apr 2022 09:13:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649434425; 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=zcEitY10iZAiJ+J3+u8UtqIoWNDWTfj8MjNNemYgu3M=; b=TVAIMyQF/40HM6WGtubk/3SslJndD1IjwPGZd4ekZtj8FZG4pU/UaBkc2e6chNiPC6AlKS +9UAGNS0F+9rf0qgU259drvP7Nj4RpJNBni867rzhIiybO5ENs5rYnHP29y6XomYeqIjgB TKwQ2zpPfeGAK1rvYDwc6op0ay3+3rM= 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-388-azkfzhqJNHiLfFgKTufWfQ-1; Fri, 08 Apr 2022 12:13:44 -0400 X-MC-Unique: azkfzhqJNHiLfFgKTufWfQ-1 Received: by mail-wm1-f69.google.com with SMTP id x8-20020a7bc768000000b0038e73173886so4568130wmk.6 for ; Fri, 08 Apr 2022 09:13:44 -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=zcEitY10iZAiJ+J3+u8UtqIoWNDWTfj8MjNNemYgu3M=; b=6zJc4+HxqE/I/tQQvsWS9vOvuemAcW0dmpji65YBBg9DiXyrXIGkSNDMFjEjsIG5Ir k6XxtFnxMKrIgAmtdk+pFsKgWI60zmaS66guYSHcg3UlnElM3vpfSyrP35+XAfrO5g8J LN8rwiAP3tFOwrm6oi5JNF3Eic0xuWGE4yT27Go83pzG/WrT08U82oWS64eUaO3R76Dm FkL27Zh2sDQW7GYb3YAtnusZIk1puClFQ/tGOS1tAHnhf8m0GIgUht/NXVsCMwi3ERiB LO7MBOP2uaN49ym4c6TknOqAe3cSlqByxt0/aDgTJhdK9x6VzwIBdXnfNQ9OXnrJGWai cZ6A== X-Gm-Message-State: AOAM530futK86Kr0VOf5wMIMuU/Zn9ijp1htpkSLiDLyfHD/jOiJjrjT SIP+KDSupiKUwTm0TQLpv0fZtLskIuXWTWd2My3SrgHVBOznrX5sTkcaiUs1zXqL6MA/y7IIAPI Poxh8HcmhnMqmpZAmsv8vLpc= X-Received: by 2002:a5d:6785:0:b0:204:f8f:8fab with SMTP id v5-20020a5d6785000000b002040f8f8fabmr15369341wru.353.1649434423620; Fri, 08 Apr 2022 09:13:43 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxt3Rj+zw8mIsN24LhLbQy+hWefHkvvpTKfeMVqAFvoZziJC7qiikDxng1MGBPfgLZBQiYEtg== X-Received: by 2002:a5d:6785:0:b0:204:f8f:8fab with SMTP id v5-20020a5d6785000000b002040f8f8fabmr15369313wru.353.1649434423340; Fri, 08 Apr 2022 09:13:43 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id t15-20020adfeb8f000000b002060d26c211sm14377455wrn.114.2022.04.08.09.13.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Apr 2022 09:13:43 -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 , Tetsuo Handa , Zhen Lei , linux-fbdev@vger.kernel.org Subject: [PATCH v2 3/5] fbdev: Restart conflicting fb removal loop when unregistering devices Date: Fri, 8 Apr 2022 18:13:20 +0200 Message-Id: <20220408161322.270176-4-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 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 | 29 +++++++++++++++++++---------- include/linux/fb.h | 1 - 2 files changed, 19 insertions(+), 11 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index bdd00d381bbc..bcdbbe543466 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; @@ -1576,16 +1577,28 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, * VESA, EFI, etc. A native driver will then be able to * allocate the memory range. * - * If it's not a platform device, at least print a warning. A - * fix would add code to remove the device from the system. + * Drop the lock because if the device is unregistered, its + * drivers will call to unregister_framebuffer() that takes + * this lock. */ + mutex_unlock(®istration_lock); if (dev_is_platform(device)) { - registered_fb[i]->forced_out = true; 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); - do_unregister_framebuffer(registered_fb[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. + */ + goto restart_removal; } } } @@ -1892,13 +1905,9 @@ 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) {