From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00CEFC43219 for ; Fri, 26 Apr 2019 05:33:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6670206E0 for ; Fri, 26 Apr 2019 05:33:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DDwi/tZq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729054AbfDZFdL (ORCPT ); Fri, 26 Apr 2019 01:33:11 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:44547 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725854AbfDZFdL (ORCPT ); Fri, 26 Apr 2019 01:33:11 -0400 Received: by mail-pg1-f194.google.com with SMTP id z16so1017072pgv.11 for ; Thu, 25 Apr 2019 22:33:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0BlWP+G5OWGW9mpUi7okyYbJLLGMBmtOivNIy7fAx4I=; b=DDwi/tZqqfSFaSVDCjsFOX8uVprJkxHGNToSWybSY/ZirrohPGXxFQ5l+krGNxrYtN 3S/ba+c0ZsscEq5/9N2W5wn/5fbLpvakGAdbFPUH7Iwo2927nEnbGS0vScZZidwiBMZR fZxhi9yUSkyG7Qe4WcqOqnuG6sO4w7gudmcrcWebNBRdtBjl4BZlcMYasV4/pf+cLsQq mo481jhPhxFNyexl5/seYbWVmYIfune7gWbvYLJO+ORqwTiOQQTojAoGsLfmUymrvmQ4 xO2BdDnS4qejGzXfo+192vSI8A97LysV3Xt1KimejkTp046F+KpEsmjf0F/TRB7b792z upXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0BlWP+G5OWGW9mpUi7okyYbJLLGMBmtOivNIy7fAx4I=; b=U8j3fojCRj8qWVTSFmSoXWj1t/4/1n00rMi7y5vyhvvpo79ezRh6vS3O/TkvhSZhmc FduMTZDvbEhWn7E9YzXvufTed4arX6ds+xwu7s2EAx+985sYLw9ixVXfXJFCMrbYa1Xr g+gtUj0ym20HyMaKCPJJpMaprHxswe2aZay5n0XwUA/M1BVP/WZyDwTTu+aECGHyEUtL JGOgSAzxb1ft22gWmLLezkjJnK5ptg2whZZAbBvI83OSa2GQN1PLoB2w20+Njw12z4tO mxm0floRK1JZRBD5Ss7Q9VfFKcyZ7tS3YKDTqp2A+lsR8q9G/BU/UOGLuq4wumT5cjyQ ZDeA== X-Gm-Message-State: APjAAAUpvaxcovXFZycJs266spFwSfQ1YsXN+IIur1+fiXmj3bMSADw4 2U0GVknnpiYHF42ITKLgjYg= X-Google-Smtp-Source: APXvYqzUyO1/qtvvUmS8tJE3ItFawslD6xkZGJKA5zyltJL0Mgnesyhhlb8pLaqQTWWOLWD9mE97XQ== X-Received: by 2002:a63:4a5f:: with SMTP id j31mr38851660pgl.369.1556256790373; Thu, 25 Apr 2019 22:33:10 -0700 (PDT) Received: from localhost.localdomain ([110.70.55.171]) by smtp.gmail.com with ESMTPSA id j5sm5256532pfg.186.2019.04.25.22.33.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Apr 2019 22:33:09 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky To: Petr Mladek , Steven Rostedt Cc: Andrew Morton , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCHv2 0/4] Access console drivers list under console_sem Date: Fri, 26 Apr 2019 14:32:58 +0900 Message-Id: <20190426053302.4332-1-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Normally, we grab console_sem lock before we iterate consoles list, which is necessary if we want to be race free. The only exception to this rule is console_flush_on_panic(). However, it seems that we are not fully race free - register_console() iterates console drivers list in unsafe manner in several places. E.g. the following scenarion: CPU0 CPU1 register_console() unregister_console() console_lock() for_each_console() // modify console_drivers con->foo kfree(con) I factored out register_console() and unregister_console() and now the bulk of the work is done under console_sem. Both in register and unregister paths we now have that oddly looking thing pr_info("console enabled/disabled"); console_unlock(); console_lock(); Which is not really odd, in fact. This is to make sure that we always print messages on all the consoles. v2: - removed outdated comment (Petr) - factor out register_console() and always run it under console_sem (Petr) - added a patch which enusures that we always print "console disabled' on every console, before we unregister one of them Sergey Senozhatsky (4): printk: factor out __unregister_console() code printk: remove invalid register_console() comment printk: factor out register_console() code printk: make sure we always print console disabled message kernel/printk/printk.c | 125 +++++++++++++++++++++++++---------------- 1 file changed, 76 insertions(+), 49 deletions(-) -- 2.21.0