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X-Received-From: 2607:f8b0:4864:20::541 Subject: [Qemu-devel] [PATCH 1/3] migration: fix migrate_cancel leads live_migration thread endless loop 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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" When we 'migrate_cancel' a multifd migration, live_migration thread may go into endless loop in multifd_send_pages functions. Reproduce steps: (qemu) migrate_set_capability multifd on (qemu) migrate -d url (qemu) [wait a while] (qemu) migrate_cancel Then may get live_migration 100% cpu usage in following stack: pthread_mutex_lock qemu_mutex_lock_impl multifd_send_pages multifd_queue_page ram_save_multifd_page ram_save_target_page ram_save_host_page ram_find_and_save_block ram_find_and_save_block ram_save_iterate qemu_savevm_state_iterate migration_iteration_run migration_thread qemu_thread_start start_thread clone Signed-off-by: Ivan Ren Reviewed-by: Juan Quintela --- migration/ram.c | 36 +++++++++++++++++++++++++++++------- 1 file changed, 29 insertions(+), 7 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 908517fc2b..f8908286c2 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -920,7 +920,7 @@ struct { * false. */ =20 -static void multifd_send_pages(void) +static int multifd_send_pages(void) { int i; static int next_channel; @@ -933,6 +933,11 @@ static void multifd_send_pages(void) p =3D &multifd_send_state->params[i]; =20 qemu_mutex_lock(&p->mutex); + if (p->quit) { + error_report("%s: channel %d has already quit!", __func__, i); + qemu_mutex_unlock(&p->mutex); + return -1; + } if (!p->pending_job) { p->pending_job++; next_channel =3D (i + 1) % migrate_multifd_channels(); @@ -951,9 +956,11 @@ static void multifd_send_pages(void) ram_counters.transferred +=3D transferred;; qemu_mutex_unlock(&p->mutex); qemu_sem_post(&p->sem); + + return 1; } =20 -static void multifd_queue_page(RAMBlock *block, ram_addr_t offset) +static int multifd_queue_page(RAMBlock *block, ram_addr_t offset) { MultiFDPages_t *pages =3D multifd_send_state->pages; =20 @@ -968,15 +975,19 @@ static void multifd_queue_page(RAMBlock *block, ram_a= ddr_t offset) pages->used++; =20 if (pages->used < pages->allocated) { - return; + return 1; } } =20 - multifd_send_pages(); + if (multifd_send_pages() < 0) { + return -1; + } =20 if (pages->block !=3D block) { - multifd_queue_page(block, offset); + return multifd_queue_page(block, offset); } + + return 1; } =20 static void multifd_send_terminate_threads(Error *err) @@ -1049,7 +1060,10 @@ static void multifd_send_sync_main(void) return; } if (multifd_send_state->pages->used) { - multifd_send_pages(); + if (multifd_send_pages() < 0) { + error_report("%s: multifd_send_pages fail", __func__); + return; + } } for (i =3D 0; i < migrate_multifd_channels(); i++) { MultiFDSendParams *p =3D &multifd_send_state->params[i]; @@ -1058,6 +1072,12 @@ static void multifd_send_sync_main(void) =20 qemu_mutex_lock(&p->mutex); =20 + if (p->quit) { + error_report("%s: channel %d has already quit", __func__, i); + qemu_mutex_unlock(&p->mutex); + return; + } + p->packet_num =3D multifd_send_state->packet_num++; p->flags |=3D MULTIFD_FLAG_SYNC; p->pending_job++; @@ -2000,7 +2020,9 @@ static int ram_save_page(RAMState *rs, PageSearchStat= us *pss, bool last_stage) static int ram_save_multifd_page(RAMState *rs, RAMBlock *block, ram_addr_t offset) { - multifd_queue_page(block, offset); + if (multifd_queue_page(block, offset) < 0) { + return -1; 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X-Received-From: 2607:f8b0:4864:20::642 Subject: [Qemu-devel] [PATCH 2/3] migration: fix migrate_cancel leads live_migration thread hung forever 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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" When we 'migrate_cancel' a multifd migration, live_migration thread may hung forever at some points, because of multifd_send_thread has already exit for socket error: 1. multifd_send_pages may hung at qemu_sem_wait(&multifd_send_state-> channels_ready) 2. multifd_send_sync_main my hung at qemu_sem_wait(&multifd_send_state-> sem_sync) Signed-off-by: Ivan Ren Reviewed-by: Juan Quintela --- migration/ram.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index f8908286c2..e4eb9c441f 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1097,7 +1097,11 @@ static void *multifd_send_thread(void *opaque) { MultiFDSendParams *p =3D opaque; Error *local_err =3D NULL; - int ret; + int ret =3D 0; + + uint32_t used =3D 0; + uint64_t packet_num =3D 0; + uint32_t flags =3D 0; =20 trace_multifd_send_thread_start(p->id); rcu_register_thread(); @@ -1113,9 +1117,9 @@ static void *multifd_send_thread(void *opaque) qemu_mutex_lock(&p->mutex); =20 if (p->pending_job) { - uint32_t used =3D p->pages->used; - uint64_t packet_num =3D p->packet_num; - uint32_t flags =3D p->flags; + used =3D p->pages->used; + packet_num =3D p->packet_num; + flags =3D p->flags; =20 p->next_packet_size =3D used * qemu_target_page_size(); multifd_send_fill_packet(p); @@ -1164,6 +1168,17 @@ out: multifd_send_terminate_threads(local_err); } =20 + /* + * Error happen, I will exit, but I can't just leave, tell + * who pay attention to me. + */ + if (ret !=3D 0) { + if (flags & MULTIFD_FLAG_SYNC) { + qemu_sem_post(&multifd_send_state->sem_sync); + } + qemu_sem_post(&multifd_send_state->channels_ready); + } + qemu_mutex_lock(&p->mutex); p->running =3D false; qemu_mutex_unlock(&p->mutex); 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X-Received-From: 2607:f8b0:4864:20::643 Subject: [Qemu-devel] [PATCH 3/3] migration: fix migrate_cancel multifd migration leads destination hung forever 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: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" When migrate_cancel a multifd migration, if run sequence like this: [source] [destination] multifd_send_sync_main[finish] multifd_recv_thread wait &p->sem_sync shutdown to_dst_file detect error from_src_file send RAM_SAVE_FLAG_EOS[fail] [no chance to run multifd_recv_sync_mai= n] multifd_load_cleanup join multifd receive thread forever will lead destination qemu hung at following stack: pthread_join qemu_thread_join multifd_load_cleanup process_incoming_migration_co coroutine_trampoline Signed-off-by: Ivan Ren --- migration/ram.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/migration/ram.c b/migration/ram.c index e4eb9c441f..504c8ccb03 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1291,6 +1291,11 @@ int multifd_load_cleanup(Error **errp) MultiFDRecvParams *p =3D &multifd_recv_state->params[i]; =20 if (p->running) { + /* + * multifd_recv_thread may hung at MULTIFD_FLAG_SYNC handle co= de, + * however try to wakeup it without harm in cleanup phase. + */ + qemu_sem_post(&p->sem_sync); qemu_thread_join(&p->thread); } object_unref(OBJECT(p->c)); --=20 2.17.2 (Apple Git-113)