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=-4.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 A5213C433B4 for ; Wed, 14 Apr 2021 14:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 81103611B0 for ; Wed, 14 Apr 2021 14:54:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231834AbhDNOyv (ORCPT ); Wed, 14 Apr 2021 10:54:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349698AbhDNOyW (ORCPT ); Wed, 14 Apr 2021 10:54:22 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2370BC06135F; Wed, 14 Apr 2021 07:52:34 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id nm3-20020a17090b19c3b029014e1bbf6c60so6777889pjb.4; Wed, 14 Apr 2021 07:52:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=4XkoYmFRvVingy29s62AE9pk1GqT7aCUqM2F6T8eWVM=; b=DyzuIz36gghGh4Pb3zLXl9BcGYmCU8qvrO4YeLUK28ps26SIYJpJsPTAy41zxtetxQ 5+W1/6kjnMpXSTZbe8NWTLWTv3v5hkfGPvcJclPuTcSMKiMm61BSUQOzlQgtkVjHEGEz QFz1qefcFcd4qzw8IvJJeGfSyqy4jt/R4vo/W51ByR380cyRXUOEWAplygfaJFIwyhcg +OJlJ3OEEI/LVu5SeteTtt0kfLDgKjEL7iz6Ut2Yrx+AB0TFIrIofTZ0McKL8V+7Ufcz H4pwouzMEbU4docKvhHRe9syXcZCAk1GRMo45tWmLLE2oZ61Q0VuC5B5Rpr8vjNVP+tV fd3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=4XkoYmFRvVingy29s62AE9pk1GqT7aCUqM2F6T8eWVM=; b=BRHmSComEwj292g5CX5pFAu0q/KAE6mNbWlIjupcsSRBp9MOcbtwA+CwuvK6FFV8hO I8VrVmXUY1oa75rJpAIq8hfH5AUpqQ9WypfI8/P3FA813gkUo1GthdjdCGZSZCkKBg0M nbkDcUeMQWa59f4w18EfD+ljzONjviFYLXm2eNPkWFIH2SwjePXHHIh+25ohqaMsKDTp OQG4mBvKjMfRUq8sA7l7C9EuBl4qyqhEYhSWadIfoPoEc6eFmGCgGB9T8reWLY1DAfWi D8auM1TAGZwTVUW5+W1rCQriBz5eE/SkAlD9UNmMtxBIr8eKZwVjybrlvLIfQoYq7el3 IdEA== X-Gm-Message-State: AOAM533JUmy9mD1uZXHpsPkLBVqBPtoU19YUSU+y4b+Y3ayktuF2opsG 8NvfDjzarQsE/+svT9dQwmg= X-Google-Smtp-Source: ABdhPJxLe4e3ArNLjIvLa46OtcJYqVPrwLT/5Pq8idpyDrx0xtUMIBXQOG/IjgfkpMbzcIBVAJl8/A== X-Received: by 2002:a17:90a:fb89:: with SMTP id cp9mr3959882pjb.47.1618411953609; Wed, 14 Apr 2021 07:52:33 -0700 (PDT) Received: from slime ([139.198.121.254]) by smtp.gmail.com with ESMTPSA id e13sm7639837pfd.64.2021.04.14.07.52.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Apr 2021 07:52:33 -0700 (PDT) From: xiaojun.zhao141@gmail.com X-Google-Original-From: Date: Wed, 14 Apr 2021 22:52:28 +0800 To: Miroslav Benes Cc: xiaojun.zhao141@gmail.com, josef@toxicpanda.com, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: the qemu-nbd process automatically exit with the commit 43347d56c 'livepatch: send a fake signal to all blocking tasks' Message-ID: <20210414225228.436ae00d@slime> In-Reply-To: References: <20210414115548.0cdb529b@slime> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Wed, 14 Apr 2021 13:27:43 +0200 (CEST) Miroslav Benes wrote: > Hi, > > On Wed, 14 Apr 2021, xiaojun.zhao141@gmail.com wrote: > > > I found the qemu-nbd process(started with qemu-nbd -t -c /dev/nbd0 > > nbd.qcow2) will automatically exit when I patched for functions of > > the nbd with livepatch. > > > > The nbd relative source: > > static int nbd_start_device_ioctl(struct nbd_device *nbd, struct > > block_device *bdev) > > { struct nbd_config *config = > > nbd->config; int > > ret; > > ret = > > nbd_start_device(nbd); if > > (ret) return > > ret; > > if > > (max_part) bdev->bd_invalidated = > > 1; > > mutex_unlock(&nbd->config_lock); ret = > > wait_event_interruptible(config->recv_wq, > > atomic_read(&config->recv_threads) == 0); if > > (ret) > > sock_shutdown(nbd); > > flush_workqueue(nbd->recv_workq); > > mutex_lock(&nbd->config_lock); > > nbd_bdev_reset(bdev); > > /* user requested, ignore socket errors > > */ if (test_bit(NBD_RT_DISCONNECT_REQUESTED, > > &config->runtime_flags)) ret = > > 0; if (test_bit(NBD_RT_TIMEDOUT, > > &config->runtime_flags)) ret = > > -ETIMEDOUT; return > > ret; } > > So my understanding is that ndb spawns a number > (config->recv_threads) of workqueue jobs and then waits for them to > finish. It waits interruptedly. Now, any signal would make > wait_event_interruptible() to return -ERESTARTSYS. Livepatch fake > signal is no exception there. The error is then propagated back to > the userspace. Unless a user requested a disconnection or there is > timeout set. How does the userspace then reacts to it? Is > _interruptible there because the userspace sends a signal in case of > NBD_RT_DISCONNECT_REQUESTED set? How does the userspace handles > ordinary signals? This all sounds a bit strange, but I may be missing > something easily. > Sorry, now I also don't know how the qemu-nbd handles these signals. I need to see its source. Thank you very much. > > When the nbd waits for atomic_read(&config->recv_threads) == 0, the > > klp will send a fake signal to it then the qemu-nbd process exits. > > And the signal of sysfs to control this action was removed in the > > commit 10b3d52790e 'livepatch: Remove signal sysfs attribute'. Are > > there other ways to control this action? How? > > No, there is no way currently. We send a fake signal automatically. > > Regards > Miroslav