Fix a segmentation fault in multifd when rb->receivedmap is cleared
too early.
After commit 5ef7e26bdb ("migration/multifd: solve zero page causing
multiple page faults"), multifd started using the rb->receivedmap
bitmap, which belongs to ram.c and is initialized and *freed* from the
ram SaveVMHandlers.
Multifd threads are live until migration_incoming_state_destroy(),
which is called after qemu_loadvm_state_cleanup(), leading to a crash
when accessing rb->receivedmap.
process_incoming_migration_co() ...
qemu_loadvm_state() multifd_nocomp_recv()
qemu_loadvm_state_cleanup() ramblock_recv_bitmap_set_offset()
rb->receivedmap = NULL set_bit_atomic(..., rb->receivedmap)
...
migration_incoming_state_destroy()
multifd_recv_cleanup()
multifd_recv_terminate_threads(NULL)
Move the loadvm cleanup into migration_incoming_state_destroy(), after
multifd_recv_cleanup() to ensure multifd thread have already exited
when rb->receivedmap is cleared.
The have_listen_thread logic can now be removed because its purpose
was to delay cleanup until postcopy_ram_listen_thread() had finished.
CC: qemu-sta...@nongnu.org
Fixes: 5ef7e26bdb ("migration/multifd: solve zero page causing multiple page
faults")
Signed-off-by: Fabiano Rosas <faro...@suse.de>
---
migration/migration.c | 1 +
migration/migration.h | 1 -
migration/savevm.c | 9 ---------
3 files changed, 1 insertion(+), 10 deletions(-)
diff --git a/migration/migration.c b/migration/migration.c
index 3dea06d577..b190a574b1 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -378,6 +378,7 @@ void migration_incoming_state_destroy(void)
struct MigrationIncomingState *mis = migration_incoming_get_current();
multifd_recv_cleanup();
+ qemu_loadvm_state_cleanup();
if (mis->to_src_file) {
/* Tell source that we are done */
diff --git a/migration/migration.h b/migration/migration.h
index 38aa1402d5..20b0a5b66e 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -101,7 +101,6 @@ struct MigrationIncomingState {
/* Set this when we want the fault thread to quit */
bool fault_thread_quit;
- bool have_listen_thread;
QemuThread listen_thread;
/* For the kernel to send us notifications */
diff --git a/migration/savevm.c b/migration/savevm.c
index d0759694fd..532ee5e4b0 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2076,10 +2076,8 @@ static void *postcopy_ram_listen_thread(void *opaque)
* got a bad migration state).
*/
migration_incoming_state_destroy();
- qemu_loadvm_state_cleanup();
rcu_unregister_thread();
- mis->have_listen_thread = false;
postcopy_state_set(POSTCOPY_INCOMING_END);
object_unref(OBJECT(migr));
@@ -2130,7 +2128,6 @@ static int
loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
return -1;
}
- mis->have_listen_thread = true;
postcopy_thread_create(mis, &mis->listen_thread, "mig/dst/listen",
postcopy_ram_listen_thread, QEMU_THREAD_DETACHED);
trace_loadvm_postcopy_handle_listen("return");
@@ -2978,11 +2975,6 @@ int qemu_loadvm_state(QEMUFile *f)
trace_qemu_loadvm_state_post_main(ret);
- if (mis->have_listen_thread) {
- /* Listen thread still going, can't clean up yet */
- return ret;
- }
-
if (ret == 0) {
ret = qemu_file_get_error(f);
}
@@ -3022,7 +3014,6 @@ int qemu_loadvm_state(QEMUFile *f)
}
}
- qemu_loadvm_state_cleanup();
cpu_synchronize_all_post_init();
return ret;
--
2.35.3
