From patchwork Wed Apr 6 21:39:17 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: 558995 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 BB0E8C433F5 for ; Wed, 6 Apr 2022 21:49:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236292AbiDFVvf (ORCPT ); Wed, 6 Apr 2022 17:51:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233507AbiDFVvL (ORCPT ); Wed, 6 Apr 2022 17:51:11 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 66ABE8C7D8 for ; Wed, 6 Apr 2022 14:40:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649281255; 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=KV4A7vxPY5Ri/A7ExTRv30H1oUVvMjyO4SRhZ4A4Rkc=; b=XMC3DO44F13IS1QdQwPv660gawUPeVr7VoCzC3L6fgK8nJcOt+V/TXyPx+Qxwez9zyi9+G 27TGLvWnJWHKluKduDBoYLSkVgWoDknJx/RI0bFmjAKmStwH9/i2iV0cL89i4LXuPBgx7E mJdYz4Jq9dnjHlU89qU+TLMixvrjfwM= 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-256-jC2uqHHgN0KwAHWUhI2KMA-1; Wed, 06 Apr 2022 17:40:55 -0400 X-MC-Unique: jC2uqHHgN0KwAHWUhI2KMA-1 Received: by mail-wm1-f71.google.com with SMTP id n21-20020a05600c4f9500b0038e3b0aa367so2430216wmq.1 for ; Wed, 06 Apr 2022 14:40:54 -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=KV4A7vxPY5Ri/A7ExTRv30H1oUVvMjyO4SRhZ4A4Rkc=; b=RuxmEowZnEOCDpUtmV126gAEs82qx/v9XxvG1NAR27V+8rgeNt9gkKYwYpnuLD4ScJ mDFdKq9wH5LwcIYilagyq9fkY8YdSG00FT+wd7CQPZycWwyjsKLPsKaiPrRK5NDJi6Jc yZ92+YJH+K7yNrQHa/HlWqX7kCM6K/0GMNguR3qH2UL3mf1Wq5eb4GrzDYRA2CIR2FNT 27RZhZAVwYrrpiURyL8FPxDC7KaxFydslfJWv23t0kF2JS+IccmofnN2v9NyXSO0Tg4H y07pG5e4jdP19kf0T8HFYTUISzPnCBPOVDHKiEHkDPuxpMygQNsHXTkm0+TwEpf5EzFc mntA== X-Gm-Message-State: AOAM532ZblWZladOQs2qAUMMwjjj4RbIeFIrGWdFCUJjgCfXIz8mzf6d /3TIzaq/N5TUS0rHntk1/inb4Y/0AVlI3FAcOC3st09htDUCsS5kL79fDaYJZOeAfCLgKax/lmw uYn506ejxMlPDj/oUVk8vtL0= X-Received: by 2002:adf:d1e8:0:b0:206:fdb:849 with SMTP id g8-20020adfd1e8000000b002060fdb0849mr8274608wrd.251.1649281253648; Wed, 06 Apr 2022 14:40:53 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz/mJZqMWnMsmiDK/QHEbj6zIloBdqX55fsoP+DxKAu2//ICDmt3KL7sczE6heg786RoMwiDQ== X-Received: by 2002:adf:d1e8:0:b0:206:fdb:849 with SMTP id g8-20020adfd1e8000000b002060fdb0849mr8274601wrd.251.1649281253422; Wed, 06 Apr 2022 14:40:53 -0700 (PDT) Received: from minerva.home ([92.176.231.205]) by smtp.gmail.com with ESMTPSA id o29-20020a05600c511d00b0038e3532b23csm5876020wms.15.2022.04.06.14.40.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Apr 2022 14:40:53 -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 , Geert Uytterhoeven , Guenter Roeck , Helge Deller , Sam Ravnborg , Xiyu Yang , Zhen Lei , Zheyu Ma , linux-fbdev@vger.kernel.org Subject: [RESEND RFC PATCH 3/5] fbdev: Restart conflicting fb removal loop when unregistering devices Date: Wed, 6 Apr 2022 23:39:17 +0200 Message-Id: <20220406213919.600294-4-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 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 --- drivers/video/fbdev/core/fbmem.c | 21 ++++++++++++++------- include/linux/fb.h | 1 - 2 files changed, 14 insertions(+), 8 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index b585339509b0..c1bfb8df9cba 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1555,6 +1555,7 @@ 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; @@ -1582,8 +1583,18 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a, * fix would add code to remove the device from the system. */ if (dev_is_platform(device)) { - registered_fb[i]->forced_out = true; + /* + * Drop the lock since the driver will call to the + * unregister_framebuffer() function that takes it. + */ + mutex_unlock(®istration_lock); platform_device_unregister(to_platform_device(device)); + mutex_lock(®istration_lock); + /* + * Restart the removal now that the platform device + * has been unregistered and its associated fb gone. + */ + goto restart_removal; } else { pr_warn("fb%d: cannot remove device\n", i); do_unregister_framebuffer(registered_fb[i]); @@ -1917,13 +1928,9 @@ 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 39baa9a70779..f1e0cd751b06 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -503,7 +503,6 @@ 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) {