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migration: split migration_incoming_co

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Originally, migration_incoming_co was introduced by
25d0c16f62
   "migration: Switch to COLO process after finishing loadvm"
to be able to enter from COLO code to one specific yield point, added
by 25d0c16f62.

Later in 923709896b
 "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 8e48ac9586
 "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>
Message-Id: <20230515130640.46035-3-vsementsov@yandex-team.ru>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2023-05-15 16:06:39 +03:00 • committed by Juan Quintela
parent 6c1e3906ce
commit dd42ce24a3
4 changed files with 18 additions and 8 deletions
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9
migration/migration.h
View file

@ -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;
/*