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=-2.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 9CFBBC43387 for ; Tue, 8 Jan 2019 18:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6FC9820685 for ; Tue, 8 Jan 2019 18:20:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=tycho-ws.20150623.gappssmtp.com header.i=@tycho-ws.20150623.gappssmtp.com header.b="iXsZyNBt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729405AbfAHSU1 (ORCPT ); Tue, 8 Jan 2019 13:20:27 -0500 Received: from mail-io1-f65.google.com ([209.85.166.65]:33430 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729168AbfAHSU1 (ORCPT ); Tue, 8 Jan 2019 13:20:27 -0500 Received: by mail-io1-f65.google.com with SMTP id t24so3922738ioi.0 for ; Tue, 08 Jan 2019 10:20:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tycho-ws.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=GoZZb+GZECSGn7r2Db9cIHtoybIpjfjGF6PsAUEXfZI=; b=iXsZyNBtX3esfm9yvpb2yZk0zgU823/fSKfrkMQpv/d8Iosc7UhNIq2Aeb87A0MJm6 QcjIk3ElqSHgnuUTl6n5f/YZNKNGO3grcEC6Rj0l+XgdtCS9N07fiM6WxZrlA9EEdQlH VCtH8bNO6YBqIhEOpPTsL05lasmTNXfBuZjefndvPa7a0w549ISdYOQDOedIIed746zS K1uDgj4qsMsRgSVbwk0ZshWrR/2fgbnjSLtZ94ndHdrWgXCLysvbuqbCzwRkW0/j498f xUxdaaTdu1s+QldDBMd+heM09smbVIVvfVgKEHEcJSXdiubKkq2uDaIHsjrJdNmKNUnQ VZmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=GoZZb+GZECSGn7r2Db9cIHtoybIpjfjGF6PsAUEXfZI=; b=aNiPSH2ec6NTFI5qbo9GXQU6qdk+EdZnkaQwwptTz9Oexkv2b1+kf0briOZolY38P6 q0fsOYjW8CtQXoj6VmDYl7/yBZXOWyHh/C0MtYi8LjqaJ6FkKlm8YUZhLgFfAHvxgryZ mmjYNM2DKVLmWEaraYYHlzg5PtnLGZimcR/Iebxa34g1ZqBHXIC3vEXPf4ZA8BNGuudz MPOwQ9W13lCHRfXo6nmfANL37EE+XfG6odSLBxvIHhZtBRwDg7MEDjtqnDQ9OOyTfkuV 0yxD1E8DDjopu8dnU94GDLlvGUXkasF58VsPoq+AJoSr0pChPeiid1Ra3Mpdm/OSSczq 9bBg== X-Gm-Message-State: AJcUukfjwEK8ufoJghvfWeVEUmdIAB5d+VKJvJPJtbnTc0QFlD5YFmw5 V1cOyPFebU00l1Ic0W2y8vQomw== X-Google-Smtp-Source: ALg8bN7bfFUCXYeGHcvkqk8/fOMH/lEj9OCuA+Ii66khZPNjZJ3TLTzffjJor9ofrr/3b5knn2RBGQ== X-Received: by 2002:a6b:c3ca:: with SMTP id t193mr1622195iof.269.1546971626076; Tue, 08 Jan 2019 10:20:26 -0800 (PST) Received: from cisco ([2601:282:901:dd7b:c092:9114:ac14:211f]) by smtp.gmail.com with ESMTPSA id 85sm31471927iou.8.2019.01.08.10.20.24 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 08 Jan 2019 10:20:25 -0800 (PST) Date: Tue, 8 Jan 2019 11:20:23 -0700 From: Tycho Andersen To: "Serge E. Hallyn" Cc: Christian Brauner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, luto@kernel.org, arnd@arndb.de, keescook@chromium.org, akpm@linux-foundation.org, jannh@google.com, oleg@redhat.com, cyphar@cyphar.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, dancol@google.com, timmurray@google.com, fweimer@redhat.com, tglx@linutronix.de, x86@kernel.org, ebiederm@xmission.com Subject: Re: [PATCH v7 2/2] selftests: add tests for pidfd_send_signal() Message-ID: <20190108182023.GA28330@cisco> References: <20190102161654.9093-1-christian@brauner.io> <20190102161654.9093-2-christian@brauner.io> <20190108175306.GF29009@cisco> <20190108175415.GA22353@mail.hallyn.com> <20190108175843.GA26016@cisco> <20190108181742.GA22614@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190108181742.GA22614@mail.hallyn.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 08, 2019 at 12:17:42PM -0600, Serge E. Hallyn wrote: > On Tue, Jan 08, 2019 at 10:58:43AM -0700, Tycho Andersen wrote: > > On Tue, Jan 08, 2019 at 11:54:15AM -0600, Serge E. Hallyn wrote: > > > On Tue, Jan 08, 2019 at 10:53:06AM -0700, Tycho Andersen wrote: > > > > On Wed, Jan 02, 2019 at 05:16:54PM +0100, Christian Brauner wrote: > > > > > + /* > > > > > + * Stop the child so we can inspect whether we have > > > > > + * recycled pid PID_RECYCLE. > > > > > + */ > > > > > + close(pipe_fds[0]); > > > > > + ret = kill(recycled_pid, SIGSTOP); > > > > > + close(pipe_fds[1]); > > > > > + if (ret) { > > > > > + (void)wait_for_pid(recycled_pid); > > > > > + _exit(PIDFD_ERROR); > > > > > + } > > > > > > > > Sorry for being late to the party, but I wonder if this whole thing > > > > couldn't be simplified with /proc/sys/kenrel/ns_last_pid? > > > > > > no, bc it's not namespaced :) > > > > Huh? It looks like it is... > > > > static int pid_ns_ctl_handler(struct ctl_table *table, int write, > > void __user *buffer, size_t *lenp, loff_t *ppos) > > { > > struct pid_namespace *pid_ns = task_active_pid_ns(current); > > struct ctl_table tmp = *table; > > int ret, next; > > > > if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) > > return -EPERM; > > > > ... > > Oh - hah, but that's ns_last_pid. You'd want pid_max. And that one > is not namespaced. Perhaps I'm misunderstanding, but isn't the point of all this code to get the same pid again? So can't we just fork(), kill(), then set ns_last_pid to pid-1, and fork() again to re-use? Tycho