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envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org C=C3=A9dric Le Goater writes: > Hello Fabiano > > On 2/14/24 21:35, Fabiano Rosas wrote: >> C=C3=A9dric Le Goater writes: >>=20 >>> Hello Fabiano >>> >>> On 2/8/24 14:29, Fabiano Rosas wrote: >>>> C=C3=A9dric Le Goater writes: >>>> >>>>> In case of error, close_return_path_on_source() can perform a shutdown >>>>> to exit the return-path thread. However, in migrate_fd_cleanup(), >>>>> 'to_dst_file' is closed before calling close_return_path_on_source() >>>>> and the shutdown fails, leaving the source and destination waiting for >>>>> an event to occur. >>>> >>>> Hi, C=C3=A9dric >>>> >>>> Are you sure this is not caused by patch 13? >>> >>> It happens with upstream QEMU without any patch. >>=20 >> I might have taken that "shutdown fails" in the commit message too >> literaly. Anyway, I have a proposed solution: >>=20 >> -->8-- >> From 729aa7b5b7f130f756d41649fdd0862bd2e90430 Mon Sep 17 00:00:00 2001 >> From: Fabiano Rosas >> Date: Wed, 14 Feb 2024 16:45:43 -0300 >> Subject: [PATCH] migration: Join the return path thread before releasing >> to_dst_file >> MIME-Version: 1.0 >> Content-Type: text/plain; charset=3DUTF-8 >> Content-Transfer-Encoding: 8bit >>=20 >> The return path thread might hang at a blocking system call. Before >> joining the thread we might need to issue a shutdown() on the socket >> file descriptor to release it. To determine whether the shutdown() is >> necessary we look at the QEMUFile error. >>=20 >> Make sure we only clean up the QEMUFile after the return path has been >> waited for. > > Yes. That's the important part. > >> This fixes a hang when qemu_savevm_state_setup() produced an error >> that was detected by migration_detect_error(). That skips >> migration_completion() so close_return_path_on_source() would get >> stuck waiting for the RP thread to terminate. >>=20 >> At migrate_fd_cleanup() I'm keeping the relative order of joining the >> migration thread and the return path just in case. > > That doesn't look necessary. Indeed. But I don't trust the migration code, it's full of undocumented dependencies like that. > What was the reason to join the migration thread only when > s->to_dst_file is valid ? I didn't find any explicit reason looking through the history. It seems we used to rely on to_dst_file before migration_thread_running was introduced. I wouldn't mind keeping that 'if' there. Let's see what Peter thinks about it.