On Thu, Feb 03, 2022 at 03:19:48PM +0000, Dr. David Alan Gilbert wrote:
> * Peter Xu (pet...@redhat.com) wrote:
> > Postcopy create threads. A common manner is we init a sem and use it to sync
> > with the thread. Namely, we have fault_thread_sem and listen_thread_sem and
> > they're only used for this.
> >
> > Make it a shared infrastructure so it's easier to create yet another thread.
> >
>
> It might be worth a note saying you now share that sem, so you can't
> start two threads in parallel.
I'll squash this into the patch:
---8<---
diff --git a/migration/migration.h b/migration/migration.h
index 845be3463c..2a311fd8d6 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -72,7 +72,10 @@ struct MigrationIncomingState {
/* A hook to allow cleanup at the end of incoming migration */
void *transport_data;
void (*transport_cleanup)(void *data);
- /* Used to sync thread creations */
+ /*
+ * Used to sync thread creations. Note that we can't create threads in
+ * parallel with this sem.
+ */
QemuSemaphore thread_sync_sem;
/*
* Free at the start of the main state load, set as the main thread
finishes
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 099d8ed478..1a3ba1db84 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -79,6 +79,10 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error
**errp)
&pnd);
}
+/*
+ * NOTE: this routine is not thread safe, we can't call it concurrently. But it
+ * should be good enough for migration's purposes.
+ */
void postcopy_thread_create(MigrationIncomingState *mis,
QemuThread *thread, const char *name,
void *(*fn)(void *), int joinable)
---8<---
>
> Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Thanks,
--
Peter Xu
