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[93.33.23.152]) by smtp.gmail.com with ESMTPSA id s8sm26257276wrt.69.2020.05.13.04.58.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 May 2020 04:58:25 -0700 (PDT) Subject: Re: [PATCH 0/5] Introduce 'yank' oob qmp command to recover from hanging qemu To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Kevin Wolf References: <20200511114947.GJ1135885@redhat.com> <20200511120718.GD2811@work-vm> <20200511121714.GL1135885@redhat.com> <20200511154645.GI2811@work-vm> <20200512113206.62836e44@luklap> <20200512094337.GK1191162@redhat.com> <20200513103245.GD6202@linux.fritz.box> <20200513105359.GF3225@work-vm> <20200513111320.GE6202@linux.fritz.box> <20200513112630.GJ1215285@redhat.com> From: Paolo Bonzini Message-ID: <31bb69c3-5149-70cf-7527-54680b1e3f6b@redhat.com> Date: Wed, 13 May 2020 13:58:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200513112630.GJ1215285@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 01:56:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lukas Straub , qemu-block , Juan Quintela , qemu-devel , Max Reitz , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 13/05/20 13:26, Daniel P. Berrangé wrote: > Are you referring to the in-kernel NFS client hangs here ? AFAIK, it is > impossible to do anything to get out of those hangs from userspace, because > the thread is stuck in an uninterruptable sleep in kernel space. > > If using the in-QEMU NFS client, then there is a network connection that > can be yanked just like the NBD client. But it's a bad idea to yank it (and also the NBD client) because you're not sure which wites have made it to the server (and to the medium) and which haven't. Effectively, the in-QEMU NFS client and NBD client are always operating in "soft" mode, but we should always treat that as a bug (which cannot be fixed) and not a feature for read-write images. Paolo