Test that downgrading an rwlock does not result in a failure to schedule coroutines queued on the rwlock. The diagram associated with test_co_rwlock_downgrade() describes the intended behaviour, but what was observed previously corresponds to: | c1 | c2 | c3 | c4 | |--------+------------+------------+----------| | rdlock | | | | | yield | | | | | | wrlock | | | | | <queued> | | | | | | rdlock | | | | | <queued> | | | | | | wrlock | | | | | <queued> | | unlock | | | | | yield | | | | | | <dequeued> | | | | | downgrade | | | | | ... | | | | | unlock | | | | | | <dequeued> | | | | | <queued> | | This results in a failure... ERROR:../tests/test-coroutine.c:369:test_co_rwlock_downgrade: assertion failed: (c3_done) Bail out! ERROR:../tests/test-coroutine.c:369:test_co_rwlock_downgrade: assertion failed: (c3_done) ...as a result of the c3 coroutine failing to run to completion. Signed-off-by: David Edmondson <david.edmondson@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20210325112941.365238-7-pbonzini@redhat.com Message-Id: <20210309144015.557477-5-david.edmondson@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>