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Wed, 16 Aug 2023 10:25:33 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id F37AB1F855; Wed, 16 Aug 2023 14:25:29 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 77331133F2; Wed, 16 Aug 2023 14:25:28 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id aGGAEFjc3GShdwAAMHmgww (envelope-from ); Wed, 16 Aug 2023 14:25:28 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1692195930; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9t0NjDORWhTRZt2oEHyswwgUTKKL0BZEn6qCStJ0d2w=; b=YjqeTTZefzE8Gwt/UaWNkMPwP0+O19dD11bBtdnkm+aVgddFBAO9RAYA2aL2OZiZ3HZWV0 8w6Nv3mC3sjmX/uxJALpx0Cxb8qlyy1hhZHnsbYo382pDq+96M+RtvrPptb9TReMHMNeBK 4NofIlibYKlWZ+CfgyJZbVA4qpTzpDQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1692195930; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9t0NjDORWhTRZt2oEHyswwgUTKKL0BZEn6qCStJ0d2w=; b=jEaURBvwpJySjtdmN3usxPYz3Z7758KYOnoIp3AhotHiMnilMSfuXHoNA5cZW/lVnHDLe7 WwVw39XtRDUT8gDA== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Juan Quintela , Peter Xu , Wei Wang , Leonardo Bras Subject: [PATCH v4 8/8] migration: Add a wrapper to cleanup migration files Date: Wed, 16 Aug 2023 11:25:10 -0300 Message-Id: <20230816142510.5637-9-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230816142510.5637-1-farosas@suse.de> References: <20230816142510.5637-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=195.135.220.29; 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 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @suse.de) X-ZM-MESSAGEID: 1692195961891100005 Content-Type: text/plain; charset="utf-8" We currently have a pattern for cleaning up a migration QEMUFile: qemu_mutex_lock(&s->qemu_file_lock); file =3D s->file_name; s->file_name =3D NULL; qemu_mutex_unlock(&s->qemu_file_lock); migration_ioc_unregister_yank_from_file(file); qemu_file_shutdown(file); qemu_fclose(file); There are some considerations for this sequence: - we must clear the pointer under the lock, to avoid TOC/TOU bugs; - the close() and yank unregister expect be given a non-null parameter; - a close() in one thread should not race with a shutdown() in another; - we don't need to shutdown() right before close(); Create a wrapper function to make sure everything works correctly. Note: the return path didn't have a yank handler registered, I added it nonetheless for uniformity. Signed-off-by: Fabiano Rosas --- migration/migration.c | 91 +++++++++++++------------------------------ 1 file changed, 27 insertions(+), 64 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 7fec57ad7f..22ab7199e4 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -217,6 +217,26 @@ MigrationIncomingState *migration_incoming_get_current= (void) return current_incoming; } =20 +static void migration_file_release(QEMUFile **file) +{ + MigrationState *ms =3D migrate_get_current(); + QEMUFile *tmp; + + /* + * Reset the pointer before releasing it to avoid holding the lock + * for too long. + */ + WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) { + tmp =3D *file; + *file =3D NULL; + } + + if (tmp) { + migration_ioc_unregister_yank_from_file(tmp); + qemu_fclose(tmp); + } +} + void migration_incoming_transport_cleanup(MigrationIncomingState *mis) { if (mis->socket_address_list) { @@ -1155,8 +1175,6 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_savevm_state_cleanup(); =20 if (s->to_dst_file) { - QEMUFile *tmp; - trace_migrate_fd_cleanup(); qemu_mutex_unlock_iothread(); if (s->migration_thread_running) { @@ -1166,16 +1184,7 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_mutex_lock_iothread(); =20 multifd_save_cleanup(); - qemu_mutex_lock(&s->qemu_file_lock); - tmp =3D s->to_dst_file; - s->to_dst_file =3D NULL; - qemu_mutex_unlock(&s->qemu_file_lock); - /* - * Close the file handle without the lock to make sure the - * critical section won't block for long. - */ - migration_ioc_unregister_yank_from_file(tmp); - qemu_fclose(tmp); + migration_file_release(&s->to_dst_file); } =20 /* @@ -1815,38 +1824,6 @@ static int migrate_handle_rp_resume_ack(MigrationSta= te *s, uint32_t value) return 0; } =20 -/* - * Release ms->rp_state.from_dst_file (and postcopy_qemufile_src if - * existed) in a safe way. - */ -static void migration_release_dst_files(MigrationState *ms) -{ - QEMUFile *file; - - WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) { - /* - * Reset the from_dst_file pointer first before releasing it, as we - * can't block within lock section - */ - file =3D ms->rp_state.from_dst_file; - ms->rp_state.from_dst_file =3D NULL; - } - - /* - * Do the same to postcopy fast path socket too if there is. No - * locking needed because this qemufile should only be managed by - * return path thread. - */ - if (ms->postcopy_qemufile_src) { - migration_ioc_unregister_yank_from_file(ms->postcopy_qemufile_src); - qemu_file_shutdown(ms->postcopy_qemufile_src); - qemu_fclose(ms->postcopy_qemufile_src); - ms->postcopy_qemufile_src =3D NULL; - } - - qemu_fclose(file); -} - /* * Handles messages sent on the return path towards the source VM * @@ -2003,6 +1980,8 @@ static int open_return_path_on_source(MigrationState = *ms) return -1; } =20 + migration_ioc_register_yank(qemu_file_get_ioc(ms->rp_state.from_dst_fi= le)); + trace_open_return_path_on_source(); =20 qemu_thread_create(&ms->rp_state.rp_thread, "return path", @@ -2046,7 +2025,8 @@ static int await_return_path_close_on_source(Migratio= nState *ms) ret =3D ms->rp_state.error; ms->rp_state.error =3D false; =20 - migration_release_dst_files(ms); + migration_file_release(&ms->rp_state.from_dst_file); + migration_file_release(&ms->postcopy_qemufile_src); =20 trace_migration_return_path_end_after(ret); return ret; @@ -2502,26 +2482,9 @@ static MigThrError postcopy_pause(MigrationState *s) assert(s->state =3D=3D MIGRATION_STATUS_POSTCOPY_ACTIVE); =20 while (true) { - QEMUFile *file; - - /* - * Current channel is possibly broken. Release it. Note that this= is - * guaranteed even without lock because to_dst_file should only be - * modified by the migration thread. That also guarantees that the - * unregister of yank is safe too without the lock. It should be = safe - * even to be within the qemu_file_lock, but we didn't do that to = avoid - * taking more mutex (yank_lock) within qemu_file_lock. TL;DR: we= make - * the qemu_file_lock critical section as small as possible. - */ + /* Current channel is possibly broken. Release it. */ assert(s->to_dst_file); - migration_ioc_unregister_yank_from_file(s->to_dst_file); - qemu_mutex_lock(&s->qemu_file_lock); - file =3D s->to_dst_file; - s->to_dst_file =3D NULL; - qemu_mutex_unlock(&s->qemu_file_lock); - - qemu_file_shutdown(file); - qemu_fclose(file); + migration_file_release(&s->to_dst_file); =20 /* * We're already pausing, so ignore any errors on the return --=20 2.35.3