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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 E4C34C47254 for ; Tue, 5 May 2020 16:13:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD568206A4 for ; Tue, 5 May 2020 16:13:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729996AbgEEQNM (ORCPT ); Tue, 5 May 2020 12:13:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:52784 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729171AbgEEQNL (ORCPT ); Tue, 5 May 2020 12:13:11 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 380E5ABF4; Tue, 5 May 2020 16:13:12 +0000 (UTC) From: Andreas Schwab To: Vasily Averin Cc: linux-kernel@vger.kernel.org, Andrew Morton , NeilBrown , Waiman Long , Steven Rostedt , Ingo Molnar , Peter Oberparleiter Subject: Re: [PATCH 7/7] sysvipc_find_ipc should increase position index References: X-Yow: C'MON, everybody!! I've flown in LESLIE GORE and two dozen KOSHER BUTCHERS! They'll be doing intricate MILITARY MANEUVERS to the soundtrack from "OKLAHOMA"!! Date: Tue, 05 May 2020 18:13:08 +0200 In-Reply-To: (Vasily Averin's message of "Fri, 24 Jan 2020 10:03:12 +0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.91 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I think this is causing this bug (seen on 5.6.8): # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages # ipcmk -Q Message queue id: 0 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x82db8127 0 root 644 0 0 # ipcmk -Q Message queue id: 1 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x82db8127 0 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcrm -q 0 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x76d1fb2a 1 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcmk -Q Message queue id: 2 # ipcrm -q 2 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x76d1fb2a 1 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcmk -Q Message queue id: 3 # ipcrm -q 1 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 As you can see, whenever an IPC item with a low id is deleted, the items with higher ids are duplicated, as if filling a hole. Andreas. -- Andreas Schwab, SUSE Labs, schwab@suse.de GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different."