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([2001:b07:6468:f312:652c:29a6:517b:66d9]) by smtp.gmail.com with ESMTPSA id g17sm6311193wru.13.2020.02.11.10.04.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Feb 2020 10:04:23 -0800 (PST) Subject: Re: [PATCH] linux-user: un-register threads from RCU before exit To: =?UTF-8?Q?Alex_Benn=c3=a9e?= , qemu-devel@nongnu.org References: <20200211173510.16347-1-alex.bennee@linaro.org> From: Paolo Bonzini Message-ID: Date: Tue, 11 Feb 2020 19:04:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20200211173510.16347-1-alex.bennee@linaro.org> Content-Language: en-US X-MC-Unique: njru_OQ4NayTJ2e5Wx3xuQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: Riku Voipio , Laurent Vivier Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/02/20 18:35, Alex Benn=C3=A9e wrote: > Through a mechanism I don't quite yet understand we can find ourselves > with a left over RCU thread when we exit group. This is a racy failure > that occurs for example with: >=20 > alpha-linux-user running testthread > with libhowvec.so plugin > but only when run from make >=20 > This may not be the correct fix but it seems to alleviate the > symptoms. Can you explain what is the effect of this left-over thread? All threads should be terminated when the process exits and I'm not sure why the user-mode emulation is special. Paolo