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authorPeter Xu <peterx@redhat.com>2020-10-21 17:27:20 -0400
committerDr. David Alan Gilbert <dgilbert@redhat.com>2020-10-26 16:15:04 +0000
commitd246ea5039fd6d5344becd0943fcbb7f8e6bbfe7 (patch)
tree0442790f727155b1d870ceb57e0882ecafa37b0b /migration
parent0c26781c0937324d175b8105bc96ccce778d9760 (diff)
migration/postcopy: Release fd before going into 'postcopy-pause'
Logically below race could trigger with the old code: test program migration thread ------------ ---------------- wait_until('postcopy-pause') postcopy_pause() set_state('postcopy-pause') do_postcopy_recover() arm s->to_dst_file with new fd release s->to_dst_file [1] Here [1] could have released the just-installed recoverying channel. Then the migration could hang without really resuming. Instead, it should be very safe to release the fd before setting the state into 'postcopy-pause', because there's no reason for any other thread to touch it during 'postcopy-active'. Dave reported a very rare postcopy recovery hang that the migration-test program waited for the migration to complete in migrate_postcopy_complete(). We do suspect it's the same thing that we're gonna fix here. Hard to tell. However since we've noticed this, fix this irrelevant of the hang report. Cc: Dr. David Alan Gilbert <dgilbert@redhat.com> Cc: Juan Quintela <quintela@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20201021212721.440373-6-peterx@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Diffstat (limited to 'migration')
-rw-r--r--migration/migration.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/migration/migration.c b/migration/migration.c
index 5421042d4a..627f194b8b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3178,9 +3178,6 @@ static MigThrError postcopy_pause(MigrationState *s)
while (true) {
QEMUFile *file;
- migrate_set_state(&s->state, s->state,
- MIGRATION_STATUS_POSTCOPY_PAUSED);
-
/* Current channel is possibly broken. Release it. */
assert(s->to_dst_file);
qemu_mutex_lock(&s->qemu_file_lock);
@@ -3191,6 +3188,9 @@ static MigThrError postcopy_pause(MigrationState *s)
qemu_file_shutdown(file);
qemu_fclose(file);
+ migrate_set_state(&s->state, s->state,
+ MIGRATION_STATUS_POSTCOPY_PAUSED);
+
error_report("Detected IO failure for postcopy. "
"Migration paused.");