* Wei Yang (richard.weiy...@gmail.com) wrote: > On Mon, Aug 19, 2019 at 12:26:32PM +0100, Dr. David Alan Gilbert wrote: > >* Wei Yang (richardw.y...@linux.intel.com) wrote: > >> No functional change. Add default case to fix warning. > > > >I think the problem with this is that migrate_set_state uses an > >atomic_cmpxchg and so we have to be careful that the type we use > >is compatible with that. > >MigrationStatus is an enum and I think compilers are allowed to > >choose the types of that; so I'm not sure we're guaranteed > >that an enum is always OK for the atomic_cmpxchg, and if it is > > Took a look into the definition of atomic_cmpxchg, which finally calls > > * __atomic_compare_exchange_n for c++11 > * __sync_val_compare_and_swap > > Both of them take two pointers to compare and exchange its content. > > Per C99 standard, http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf, > it mentioned: > > Each enumerated type shall be compatible with char, a signed integer type, > or an unsigned integer type. The choice of type is implementation-defined, > but shall be capable of representing the values of all the members of the > enumeration. > > Based on this, I think atomic_cmpxchg should work fine with enum.
Hmm OK, but I'd need you to test n some 32bit and other comp=ilers etc; make sure it works on 32bit, clang, gcc, 32bit ARM etc - because otherwise I'm going to have to worry about checking all those. Dave > >then we also might have to make the old_state and new_state > >variables match. > > > > You are right. > >Dave > > > >> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com> > >> --- > >> migration/migration.c | 8 +++++++- > >> migration/migration.h | 6 +++--- > >> 2 files changed, 10 insertions(+), 4 deletions(-) > >> > >> diff --git a/migration/migration.c b/migration/migration.c > >> index 2865ae3fa9..0fd2364961 100644 > >> --- a/migration/migration.c > >> +++ b/migration/migration.c > >> @@ -946,6 +946,8 @@ static void fill_source_migration_info(MigrationInfo > >> *info) > >> case MIGRATION_STATUS_CANCELLED: > >> info->has_status = true; > >> break; > >> + default: > >> + return; > >> } > >> info->status = s->state; > >> } > >> @@ -1054,6 +1056,8 @@ static void > >> fill_destination_migration_info(MigrationInfo *info) > >> info->has_status = true; > >> fill_destination_postcopy_migration_info(info); > >> break; > >> + default: > >> + return; > >> } > >> info->status = mis->state; > >> } > >> @@ -1446,7 +1450,7 @@ void qmp_migrate_start_postcopy(Error **errp) > >> > >> /* shared migration helpers */ > >> > >> -void migrate_set_state(int *state, int old_state, int new_state) > >> +void migrate_set_state(MigrationStatus *state, int old_state, int > >> new_state) > >> { > >> assert(new_state < MIGRATION_STATUS__MAX); > >> if (atomic_cmpxchg(state, old_state, new_state) == old_state) { > >> @@ -1683,6 +1687,8 @@ bool migration_is_idle(void) > >> return false; > >> case MIGRATION_STATUS__MAX: > >> g_assert_not_reached(); > >> + default: > >> + g_assert_not_reached(); > >> } > >> > >> return false; > >> diff --git a/migration/migration.h b/migration/migration.h > >> index 5e8f09c6db..418ee00053 100644 > >> --- a/migration/migration.h > >> +++ b/migration/migration.h > >> @@ -65,7 +65,7 @@ struct MigrationIncomingState { > >> > >> QEMUBH *bh; > >> > >> - int state; > >> + MigrationStatus state; > >> > >> bool have_colo_incoming_thread; > >> QemuThread colo_incoming_thread; > >> @@ -151,7 +151,7 @@ struct MigrationState > >> /* params from 'migrate-set-parameters' */ > >> MigrationParameters parameters; > >> > >> - int state; > >> + MigrationStatus state; > >> > >> /* State related to return path */ > >> struct { > >> @@ -234,7 +234,7 @@ struct MigrationState > >> bool decompress_error_check; > >> }; > >> > >> -void migrate_set_state(int *state, int old_state, int new_state); > >> +void migrate_set_state(MigrationStatus *state, int old_state, int > >> new_state); > >> > >> void migration_fd_process_incoming(QEMUFile *f); > >> void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp); > >> -- > >> 2.19.1 > >> > >-- > >Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK > > -- > Wei Yang > Help you, Help me -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK