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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E4616D116F6 for ; Tue, 2 Dec 2025 12:00:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vQP34-0005DZ-IO; Tue, 02 Dec 2025 07:00:02 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vQP2y-0005DG-4U for qemu-devel@nongnu.org; Tue, 02 Dec 2025 06:59:56 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vQP2v-0004VK-OT for qemu-devel@nongnu.org; Tue, 02 Dec 2025 06:59:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764676790; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Zw87keFOa5uYYKknnfEjadLNJ8Tt85K22V05rIfTHIM=; b=X2fRt/xDMRcygGjQGbp8AxxaVNpKRg4w7w/D5OdcfvTlIJzSMevfsm3yY77azm/sh/M/bl 1AkQR08Jy0zwgU2Z23nftr0ypkiGDjHljdRQoL2e++WwNGFtIRu2fg6hrVyko7xd+6YU2E vbnE11puSjSVLcm/3Hhp0GXbrVsUyvU= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-235-j3cO9tQxPzyb9AsFfMWHtQ-1; Tue, 02 Dec 2025 06:59:47 -0500 X-MC-Unique: j3cO9tQxPzyb9AsFfMWHtQ-1 X-Mimecast-MFC-AGG-ID: j3cO9tQxPzyb9AsFfMWHtQ_1764676786 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 59B641800370; Tue, 2 Dec 2025 11:59:44 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.7]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8570919560B7; Tue, 2 Dec 2025 11:59:43 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id C4BC121E6A27; Tue, 02 Dec 2025 12:59:40 +0100 (CET) From: Markus Armbruster To: Peter Xu Cc: qemu-devel@nongnu.org, Daniel P . =?utf-8?Q?Berrang=C3=A9?= , Fabiano Rosas , Vladimir Sementsov-Ogievskiy , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Juraj Marcin Subject: Re: [PATCH for-11.0 v2 7/7] migration: Replace migrate_set_error() with migrate_error_propagate() In-Reply-To: <20251201194510.1121221-8-peterx@redhat.com> (Peter Xu's message of "Mon, 1 Dec 2025 14:45:10 -0500") References: <20251201194510.1121221-1-peterx@redhat.com> <20251201194510.1121221-8-peterx@redhat.com> Date: Tue, 02 Dec 2025 12:59:40 +0100 Message-ID: <87fr9tumab.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > migrate_set_error() currently doesn't take ownership of the error being > passed in. It's not aligned with the error API and meanwhile it also > makes most of the caller free the error explicitly. > > Change the API to take the ownership of the Error object instead. This > should save a lot of error_copy() invocations. > > Signed-off-by: Peter Xu > --- > migration/migration.h | 2 +- > migration/cpr-exec.c | 5 ++-- > migration/migration.c | 44 +++++++++++++++----------------- > migration/multifd-device-state.c | 5 +--- > migration/multifd.c | 19 +++++++------- > migration/postcopy-ram.c | 5 ++-- > migration/ram.c | 4 +-- > migration/savevm.c | 16 +++++------- > 8 files changed, 43 insertions(+), 57 deletions(-) > > diff --git a/migration/migration.h b/migration/migration.h > index 213b33fe6e..e4b4f25deb 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -525,7 +525,7 @@ void migration_incoming_process(void); > > bool migration_has_all_channels(void); > > -void migrate_set_error(MigrationState *s, const Error *error); > +void migrate_error_propagate(MigrationState *s, Error *error); > bool migrate_has_error(MigrationState *s); > > void migration_connect(MigrationState *s, Error *error_in); > diff --git a/migration/cpr-exec.c b/migration/cpr-exec.c > index 0b8344a86f..da287d8031 100644 > --- a/migration/cpr-exec.c > +++ b/migration/cpr-exec.c > @@ -158,8 +158,9 @@ static void cpr_exec_cb(void *opaque) > > error_report_err(error_copy(err)); > migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED); > - migrate_set_error(s, err); > - error_free(err); > + > + migrate_error_propagate(s, err); > + /* We must reset the error because it'll be reused later */ > err = NULL; > > /* Note, we can go from state COMPLETED to FAILED */ > diff --git a/migration/migration.c b/migration/migration.c > index 0ff8b31a88..70813e5006 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -914,9 +914,7 @@ process_incoming_migration_co(void *opaque) > fail: > migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_FAILED); > - migrate_set_error(s, local_err); > - error_free(local_err); > - > + migrate_error_propagate(s, local_err); > migration_incoming_state_destroy(); > > if (mis->exit_on_error) { > @@ -1548,14 +1546,20 @@ static void migration_cleanup_bh(void *opaque) > migration_cleanup(opaque); > } > > -void migrate_set_error(MigrationState *s, const Error *error) > +/* > + * Propagate the Error* object to migration core. The caller mustn't > + * reference the error pointer after the function returned, because the > + * Error* object might be freed. > + */ > +void migrate_error_propagate(MigrationState *s, Error *error) > { > QEMU_LOCK_GUARD(&s->error_mutex); > - > trace_migrate_error(error_get_pretty(error)); > > if (!s->error) { > - s->error = error_copy(error); > + s->error = error; > + } else { > + error_free(error); > } This is correct. Also correct, and possibly easier to understand at a glance: error_propagate(&s->error, error); error_propagate() has code for a number of additional conditions, but these are all impossible: * @error cannot be null here (because error_get_pretty(error) above) * &s->error cannot be &error_abort, &error_fatal, or null Thoughts? > } > > @@ -1601,8 +1605,7 @@ static void migration_connect_error_propagate(MigrationState *s, Error *error) > } > > migrate_set_state(&s->state, current, next); > - migrate_set_error(s, error); > - error_free(error); > + migrate_error_propagate(s, error); > } > > void migration_cancel(void) > @@ -2014,8 +2017,7 @@ void qmp_migrate_pause(Error **errp) > > /* Tell the core migration that we're pausing */ > error_setg(&error, "Postcopy migration is paused by the user"); > - migrate_set_error(ms, error); > - error_free(error); > + migrate_error_propagate(ms, error); > > qemu_mutex_lock(&ms->qemu_file_lock); > if (ms->to_dst_file) { > @@ -2647,8 +2649,7 @@ static void *source_return_path_thread(void *opaque) > > out: > if (err) { > - migrate_set_error(ms, err); > - error_free(err); > + migrate_error_propagate(ms, err); > trace_source_return_path_thread_bad_end(); > } > > @@ -3094,12 +3095,10 @@ static void migration_completion(MigrationState *s) > > fail: > if (qemu_file_get_error_obj(s->to_dst_file, &local_err)) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > } else if (ret) { > error_setg_errno(&local_err, -ret, "Error in migration completion"); > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > } > > if (s->state != MIGRATION_STATUS_CANCELLING) { > @@ -3326,8 +3325,7 @@ static MigThrError migration_detect_error(MigrationState *s) > } > > if (local_error) { > - migrate_set_error(s, local_error); > - error_free(local_error); > + migrate_error_propagate(s, local_error); > } > > if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret) { > @@ -3522,7 +3520,7 @@ static MigIterateState migration_iteration_run(MigrationState *s) > if (must_precopy <= s->threshold_size && > can_switchover && qatomic_read(&s->start_postcopy)) { > if (postcopy_start(s, &local_err)) { > - migrate_set_error(s, local_err); > + migrate_error_propagate(s, error_copy(local_err)); > error_report_err(local_err); > } > return MIG_ITERATE_SKIP; > @@ -3819,8 +3817,7 @@ static void *migration_thread(void *opaque) > * devices to unplug. This to preserve migration state transitions. > */ > if (ret) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_FAILED); > goto out; > @@ -3944,8 +3941,7 @@ static void *bg_migration_thread(void *opaque) > * devices to unplug. This to preserve migration state transitions. > */ > if (ret) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_FAILED); > goto fail_setup; > @@ -4127,7 +4123,7 @@ void migration_connect(MigrationState *s, Error *error_in) > return; > > fail: > - migrate_set_error(s, local_err); > + migrate_error_propagate(s, error_copy(local_err)); > if (s->state != MIGRATION_STATUS_CANCELLING) { > migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED); > } > diff --git a/migration/multifd-device-state.c b/migration/multifd-device-state.c > index db3239fef5..91d5d81556 100644 > --- a/migration/multifd-device-state.c > +++ b/migration/multifd-device-state.c > @@ -143,8 +143,6 @@ static int multifd_device_state_save_thread(void *opaque) > Error *local_err = NULL; > > if (!data->hdlr(data, &local_err)) { > - MigrationState *s = migrate_get_current(); > - > /* > * Can't call abort_device_state_save_threads() here since new > * save threads could still be in process of being launched > @@ -158,8 +156,7 @@ static int multifd_device_state_save_thread(void *opaque) > * In case of multiple save threads failing which thread error > * return we end setting is purely arbitrary. > */ > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(migrate_get_current(), local_err); > } > > return 0; > diff --git a/migration/multifd.c b/migration/multifd.c > index 52e4d25857..bf6da85af8 100644 > --- a/migration/multifd.c > +++ b/migration/multifd.c > @@ -428,8 +428,9 @@ static void multifd_send_error_propagate(Error *err) > > if (err) { > MigrationState *s = migrate_get_current(); > - migrate_set_error(s, err); > - error_free(err); > + > + migrate_error_propagate(s, err); > + > if (s->state == MIGRATION_STATUS_SETUP || > s->state == MIGRATION_STATUS_PRE_SWITCHOVER || > s->state == MIGRATION_STATUS_DEVICE || > @@ -588,8 +589,7 @@ void multifd_send_shutdown(void) > Error *local_err = NULL; > > if (!multifd_send_cleanup_channel(p, &local_err)) { > - migrate_set_error(migrate_get_current(), local_err); > - error_free(local_err); > + migrate_error_propagate(migrate_get_current(), local_err); > } > } > > @@ -962,8 +962,7 @@ bool multifd_send_setup(void) > p->write_flags = 0; > > if (!multifd_new_send_channel_create(p, &local_err)) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > ret = -1; > } > } > @@ -987,8 +986,7 @@ bool multifd_send_setup(void) > > ret = multifd_send_state->ops->send_setup(p, &local_err); > if (ret) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > goto err; > } > assert(p->iov); > @@ -1067,8 +1065,9 @@ static void multifd_recv_terminate_threads(Error *err) > > if (err) { > MigrationState *s = migrate_get_current(); > - migrate_set_error(s, err); > - error_free(err); > + > + migrate_error_propagate(s, err); > + > if (s->state == MIGRATION_STATUS_SETUP || > s->state == MIGRATION_STATUS_ACTIVE) { > migrate_set_state(&s->state, s->state, > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index 7c9fe61041..dd8e31f5ae 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -1927,8 +1927,7 @@ postcopy_preempt_send_channel_done(MigrationState *s, > QIOChannel *ioc, Error *local_err) > { > if (local_err) { > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(s, local_err); > } else { > migration_ioc_register_yank(ioc); > s->postcopy_qemufile_src = qemu_file_new_output(ioc); > @@ -2162,7 +2161,7 @@ static void *postcopy_listen_thread(void *opaque) > * exit depending on if postcopy-exit-on-error is true, but the > * migration cannot be recovered. > */ > - migrate_set_error(migr, local_err); > + migrate_error_propagate(migr, error_copy(local_err)); > error_report_err(local_err); > migrate_set_state(&mis->state, mis->state, MIGRATION_STATUS_FAILED); > goto out; > diff --git a/migration/ram.c b/migration/ram.c > index 29f016cb25..a2f456d858 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -4730,9 +4730,7 @@ static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host, > * Abort and indicate a proper reason. > */ > error_setg(&err, "RAM block '%s' resized during precopy.", rb->idstr); > - migrate_set_error(migrate_get_current(), err); > - error_free(err); > - > + migrate_error_propagate(migrate_get_current(), err); > migration_cancel(); > } > > diff --git a/migration/savevm.c b/migration/savevm.c > index 638e9b364f..67f10a5dbe 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1125,13 +1125,12 @@ void qemu_savevm_send_open_return_path(QEMUFile *f) > int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len) > { > uint32_t tmp; > - MigrationState *ms = migrate_get_current(); > Error *local_err = NULL; > > if (len > MAX_VM_CMD_PACKAGED_SIZE) { > error_setg(&local_err, "%s: Unreasonably large packaged state: %zu", > __func__, len); > - migrate_set_error(ms, local_err); > + migrate_error_propagate(migrate_get_current(), error_copy(local_err)); I'd break this line between the arguments. Matter of taste, up to you. > error_report_err(local_err); > return -1; > } > @@ -1373,7 +1372,7 @@ int qemu_savevm_state_setup(QEMUFile *f, Error **errp) > if (se->vmsd && se->vmsd->early_setup) { > ret = vmstate_save(f, se, vmdesc, errp); > if (ret) { > - migrate_set_error(ms, *errp); > + migrate_error_propagate(ms, error_copy(*errp)); > qemu_file_set_error(f, ret); > break; > } > @@ -1681,7 +1680,7 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f, > > ret = vmstate_save(f, se, vmdesc, &local_err); > if (ret) { > - migrate_set_error(ms, local_err); > + migrate_error_propagate(ms, error_copy(local_err)); > error_report_err(local_err); > qemu_file_set_error(f, ret); > return ret; > @@ -1858,7 +1857,6 @@ void qemu_savevm_live_state(QEMUFile *f) > > int qemu_save_device_state(QEMUFile *f) > { > - MigrationState *ms = migrate_get_current(); > Error *local_err = NULL; > SaveStateEntry *se; > > @@ -1876,7 +1874,8 @@ int qemu_save_device_state(QEMUFile *f) > } > ret = vmstate_save(f, se, NULL, &local_err); > if (ret) { > - migrate_set_error(ms, local_err); > + migrate_error_propagate(migrate_get_current(), > + error_copy(local_err)); > error_report_err(local_err); > return ret; > } > @@ -2826,8 +2825,6 @@ static int qemu_loadvm_load_thread(void *thread_opaque) > Error *local_err = NULL; > > if (!data->function(data->opaque, &mis->load_threads_abort, &local_err)) { > - MigrationState *s = migrate_get_current(); > - > /* > * Can't set load_threads_abort here since processing of main migration > * channel data could still be happening, resulting in launching of new > @@ -2840,8 +2837,7 @@ static int qemu_loadvm_load_thread(void *thread_opaque) > * In case of multiple load threads failing which thread error > * return we end setting is purely arbitrary. > */ > - migrate_set_error(s, local_err); > - error_free(local_err); > + migrate_error_propagate(migrate_get_current(), local_err); > } > > return 0; Reviewed-by: Markus Armbruster