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migration/multifd: Fix multifd_send_setup cleanup when channel creation fails 

When a channel fails to create, the code currently just returns. This
is wrong for two reasons:

1) Channel n+1 will not get to initialize it's semaphores, leading to
   an assert when terminate_threads tries to post to it:

 qemu-system-x86_64: ../util/qemu-thread-posix.c:92:
 qemu_mutex_lock_impl: Assertion `mutex->initialized' failed.

2) (theoretical) If channel n-1 already started creation it will
   defeat the purpose of the channels_created logic which is in place
   to avoid migrate_fd_cleanup() to run while channels are still being
   created.

   This cannot really happen today because the current failure cases
   for multifd_new_send_channel_create() are all synchronous,
   resulting from qio_channel_file_new_path() getting a bad
   filename. This would hit all channels equally.

   But I don't want to set a trap for future people, so have all
   channels try to create (even if failing), and only fail after the
   channels_created semaphore has been posted.

While here, remove the error_report_err call. There's one already at
migrate_fd_cleanup later on.

Cc: qemu-stable@nongnu.org
Reported-by: Jim Fehlig <jfehlig@suse.com>
Fixes: b7b03eb614 ("migration/multifd: Add outgoing QIOChannelFile support")
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This commit is contained in:
Fabiano Rosas 2024-08-01 14:41:01 -03:00
parent 84ac6fa12d
commit 0bd5b9284f
1 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
migration/multifd.c
View File

@ -1156,7 +1156,6 @@ static bool multifd_new_send_channel_create(gpointer opaque, Error **errp)
bool multifd_send_setup(void)
{
MigrationState *s = migrate_get_current();
Error *local_err = NULL;
int thread_count, ret = 0;
uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
bool use_packets = multifd_use_packets();
@ -1177,6 +1176,7 @@ bool multifd_send_setup(void)
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
Error *local_err = NULL;
qemu_sem_init(&p->sem, 0);
qemu_sem_init(&p->sem_sync, 0);
@ -1196,7 +1196,8 @@ bool multifd_send_setup(void)
p->write_flags = 0;
if (!multifd_new_send_channel_create(p, &local_err)) {
return false;
migrate_set_error(s, local_err);
ret = -1;
}
}
@ -1209,24 +1210,27 @@ bool multifd_send_setup(void)
qemu_sem_wait(&multifd_send_state->channels_created);
}
if (ret) {
goto err;
}
for (i = 0; i < thread_count; i++) {
MultiFDSendParams *p = &multifd_send_state->params[i];
Error *local_err = NULL;
ret = multifd_send_state->ops->send_setup(p, &local_err);
if (ret) {
break;
migrate_set_error(s, local_err);
goto err;
}
}
if (ret) {
migrate_set_error(s, local_err);
error_report_err(local_err);
migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_FAILED);
return false;
}
return true;
err:
migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
MIGRATION_STATUS_FAILED);
return false;
}
bool multifd_recv(void)