From patchwork Tue Feb 8 21:08:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 540956 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 B53C5C433F5 for ; Tue, 8 Feb 2022 22:23:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386941AbiBHWXc (ORCPT ); Tue, 8 Feb 2022 17:23:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1386730AbiBHVIw (ORCPT ); Tue, 8 Feb 2022 16:08:52 -0500 Received: from mail-wr1-x436.google.com (mail-wr1-x436.google.com [IPv6:2a00:1450:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3742C0612BA for ; Tue, 8 Feb 2022 13:08:51 -0800 (PST) Received: by mail-wr1-x436.google.com with SMTP id s18so572850wrv.7 for ; Tue, 08 Feb 2022 13:08:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=4vhsaJLRuFd4cLY+OipxjxgQ9+hkB2eOCoIWIkwzsX4=; b=hSTzBYbk+EsRstvMat5gULyq5OnxonnqMQZDYW4OJ03WdVZriqwshzqAMnR7z6Mxs/ W6MTAgwmuJNCwpePfGNu5wjMP+TCcIEb/7e82sC/9tyzHPsI/T9dN7TU5AUq23/yggHX dBWuat8BzdR3DTzRrJ0Hynpwp08gs8C0OyboY= 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=4vhsaJLRuFd4cLY+OipxjxgQ9+hkB2eOCoIWIkwzsX4=; b=ewnXJeUoy3kRIIlx0cI9Zj1Rl1MmnrFFXI+v/MOy7iB7lv8HcQ1GDnfL/d9itvcohY YCkOadEcAsRUo/NZ1t21FWJWeNvNg3TqjxR8z83NMMaGJnCfhnhmi10aElTQlVvPK0QG rGQbEquEMxyHgBQ/PDBUPLmlFD6GCZQEPkiBIBSFzJi6UavlbmQ8rpfNrDTGZjEiqtIC 6dYriKssi+X6sKKjoXadud1QxZ3fj/zZxvXzdxbRLCfyMGzv86r93j9NxvvOk0N9wGRr qljsJDuzFEV9XhTIuqnXMDH+JWKqwfO1f4VdQwRSH3ykzC6IrFDNraWqhq91QPlsZyfu C9Cg== X-Gm-Message-State: AOAM530dFqagxj2ftrp3R+0lcasrcoDdBA+bJCNk2W/gWKg15ThZKAdO fnjXNvrdw7liBl529tQwb1LaXw== X-Google-Smtp-Source: ABdhPJx34FaRILEJCtAru2c7l4UL1l3tfbLxaWVDlH2pbi+Y5VD+HSoJSIbcO7Y6315RPOWA+MZjag== X-Received: by 2002:a5d:5246:: with SMTP id k6mr4924929wrc.89.1644354530369; Tue, 08 Feb 2022 13:08:50 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id o14sm3033561wmr.3.2022.02.08.13.08.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Feb 2022 13:08:49 -0800 (PST) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , linux-fbdev@vger.kernel.org, LKML , Daniel Vetter , Sam Ravnborg , Daniel Vetter , Daniel Vetter , Claudio Suarez , Tetsuo Handa , Thomas Zimmermann , Greg Kroah-Hartman , Du Cheng , Matthew Wilcox , William Kucharski , Alex Deucher , Zheyu Ma , Zhen Lei , Xiyu Yang Subject: [PATCH v2 12/19] fbcon: use lock_fb_info in fbcon_open/release Date: Tue, 8 Feb 2022 22:08:17 +0100 Message-Id: <20220208210824.2238981-13-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220208210824.2238981-1-daniel.vetter@ffwll.ch> References: <20220208210824.2238981-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Now we get to the real motiviation, because fbmem.c insists that that's the right lock for these. Ofc fbcon.c has a lot more places where it probably should call lock_fb_info(). But looking at fbmem.c at least most of these seem to be protected by console_lock() too, which is probably what papers over any issues. Note that this means we're shuffling around a bit the locking sections for some of the console takeover and unbind paths, but not all: - console binding/unbinding from the console layer never with lock_fb_info - unbind (as opposed to unlink) never bother with lock_fb_info Also the real serialization against set_par and set_pan are still doing by wrapping the entire ioctl code in console_lock(). So this shuffling shouldn't be worse than what we had from a "can you trigger races?" pov, but it's at least clearer. Acked-by: Sam Ravnborg Signed-off-by: Daniel Vetter Cc: Daniel Vetter Cc: Claudio Suarez Cc: Tetsuo Handa Cc: Thomas Zimmermann Cc: Greg Kroah-Hartman Cc: Du Cheng Cc: Sam Ravnborg Cc: Matthew Wilcox Cc: William Kucharski Cc: Alex Deucher Cc: Zheyu Ma Cc: Zhen Lei Cc: Xiyu Yang --- drivers/video/fbdev/core/fbcon.c | 5 +++++ drivers/video/fbdev/core/fbmem.c | 4 ---- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index f0213a0e3870..cc960bf49991 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -684,8 +684,10 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount) static void fbcon_release(struct fb_info *info) { + lock_fb_info(info); if (info->fbops->fb_release) info->fbops->fb_release(info, 0); + unlock_fb_info(info); module_put(info->fbops->owner); } @@ -697,11 +699,14 @@ static int fbcon_open(struct fb_info *info) if (!try_module_get(info->fbops->owner)) return -ENODEV; + lock_fb_info(info); if (info->fbops->fb_open && info->fbops->fb_open(info, 0)) { + unlock_fb_info(info); module_put(info->fbops->owner); return -ENODEV; } + unlock_fb_info(info); ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL); if (!ops) { diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index ad9aac06427a..37656883e7bd 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1674,9 +1674,7 @@ static int do_register_framebuffer(struct fb_info *fb_info) console_lock(); else atomic_inc(&ignore_console_lock_warning); - lock_fb_info(fb_info); ret = fbcon_fb_registered(fb_info); - unlock_fb_info(fb_info); if (!lockless_register_fb) console_unlock(); @@ -1693,9 +1691,7 @@ static void unbind_console(struct fb_info *fb_info) return; console_lock(); - lock_fb_info(fb_info); fbcon_fb_unbind(fb_info); - unlock_fb_info(fb_info); console_unlock(); }