| Message ID | 20230515130640.46035-3-vsementsov@yandex-team.ru (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | COLO: improve build options | expand |
Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> wrote: > Originally, migration_incoming_co was introduced by > 25d0c16f625feb3b6 > "migration: Switch to COLO process after finishing loadvm" > to be able to enter from COLO code to one specific yield point, added > by 25d0c16f625feb3b6. > > Later in 923709896b1b0 > "migration: poll the cm event for destination qemu" > we reused this variable to wake the migration incoming coroutine from > RDMA code. > > That was doubtful idea. Entering coroutines is a very fragile thing: > you should be absolutely sure which yield point you are going to enter. > > I don't know how much is it safe to enter during qemu_loadvm_state() > which I think what RDMA want to do. But for sure RDMA shouldn't enter > the special COLO-related yield-point. As well, COLO code doesn't want > to enter during qemu_loadvm_state(), it want to enter it's own specific > yield-point. > > As well, when in 8e48ac95865ac97d > "COLO: Add block replication into colo process" we added > bdrv_invalidate_cache_all() call (now it's called activate_all()) > it became possible to enter the migration incoming coroutine during > that call which is wrong too. > > So, let't make these things separate and disjoint: loadvm_co for RDMA, > non-NULL during qemu_loadvm_state(), and colo_incoming_co for COLO, > non-NULL only around specific yield. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Reviewed-by: Juan Quintela <quintela@redhat.com>
diff --git a/migration/colo.c b/migration/colo.c index 6c7c313956..a688ac553a 100644 --- a/migration/colo.c +++ b/migration/colo.c @@ -145,8 +145,8 @@ static void secondary_vm_do_failover(void) qemu_sem_post(&mis->colo_incoming_sem); /* For Secondary VM, jump to incoming co */ - if (mis->migration_incoming_co) { - qemu_coroutine_enter(mis->migration_incoming_co); + if (mis->colo_incoming_co) { + qemu_coroutine_enter(mis->colo_incoming_co); } } diff --git a/migration/migration.c b/migration/migration.c index 439e8651df..e66b06d3ec 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -520,12 +520,14 @@ process_incoming_migration_co(void *opaque) goto fail; } - mis->migration_incoming_co = qemu_coroutine_self(); mis->largest_page_size = qemu_ram_pagesize_largest(); postcopy_state_set(POSTCOPY_INCOMING_NONE); migrate_set_state(&mis->state, MIGRATION_STATUS_NONE, MIGRATION_STATUS_ACTIVE); + + mis->loadvm_co = qemu_coroutine_self(); ret = qemu_loadvm_state(mis->from_src_file); + mis->loadvm_co = NULL; ps = postcopy_state_get(); trace_process_incoming_migration_co_end(ret, ps); @@ -566,7 +568,10 @@ process_incoming_migration_co(void *opaque) qemu_thread_create(&colo_incoming_thread, "COLO incoming", colo_process_incoming_thread, mis, QEMU_THREAD_JOINABLE); + + mis->colo_incoming_co = qemu_coroutine_self(); qemu_coroutine_yield(); + mis->colo_incoming_co = NULL; qemu_mutex_unlock_iothread(); /* Wait checkpoint incoming thread exit before free resource */ @@ -578,7 +583,6 @@ process_incoming_migration_co(void *opaque) mis->bh = qemu_bh_new(process_incoming_migration_bh, mis); qemu_bh_schedule(mis->bh); - mis->migration_incoming_co = NULL; return; fail: local_err = NULL; diff --git a/migration/migration.h b/migration/migration.h index 7721c7658b..48a46123a0 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -162,8 +162,15 @@ struct MigrationIncomingState { int state; + /* + * The incoming migration coroutine, non-NULL during qemu_loadvm_state(). + * Used to wake the migration incoming coroutine from rdma code. How much is + * it safe - it's a question. + */ + Coroutine *loadvm_co; + /* The coroutine we should enter (back) after failover */ - Coroutine *migration_incoming_co; + Coroutine *colo_incoming_co; QemuSemaphore colo_incoming_sem; /* diff --git a/migration/rdma.c b/migration/rdma.c index 2cd8f1cc66..2e4dcff1c9 100644 --- a/migration/rdma.c +++ b/migration/rdma.c @@ -3342,9 +3342,8 @@ static void rdma_cm_poll_handler(void *opaque) } } rdma_ack_cm_event(cm_event); - - if (mis->migration_incoming_co) { - qemu_coroutine_enter(mis->migration_incoming_co); + if (mis->loadvm_co) { + qemu_coroutine_enter(mis->loadvm_co); } return; }
Originally, migration_incoming_co was introduced by 25d0c16f625feb3b6 "migration: Switch to COLO process after finishing loadvm" to be able to enter from COLO code to one specific yield point, added by 25d0c16f625feb3b6. Later in 923709896b1b0 "migration: poll the cm event for destination qemu" we reused this variable to wake the migration incoming coroutine from RDMA code. That was doubtful idea. Entering coroutines is a very fragile thing: you should be absolutely sure which yield point you are going to enter. I don't know how much is it safe to enter during qemu_loadvm_state() which I think what RDMA want to do. But for sure RDMA shouldn't enter the special COLO-related yield-point. As well, COLO code doesn't want to enter during qemu_loadvm_state(), it want to enter it's own specific yield-point. As well, when in 8e48ac95865ac97d "COLO: Add block replication into colo process" we added bdrv_invalidate_cache_all() call (now it's called activate_all()) it became possible to enter the migration incoming coroutine during that call which is wrong too. So, let't make these things separate and disjoint: loadvm_co for RDMA, non-NULL during qemu_loadvm_state(), and colo_incoming_co for COLO, non-NULL only around specific yield. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> --- migration/colo.c | 4 ++-- migration/migration.c | 8 ++++++-- migration/migration.h | 9 ++++++++- migration/rdma.c | 5 ++--- 4 files changed, 18 insertions(+), 8 deletions(-)