In another attempt to further isolate the system parameters that trigger the issue, I set up a couple of minimal systems using various combinations of dmcrypt and raid1. As it turned out, having raid1 enabled is sufficient for triggering the issue, so commit e22bee782b3b00bd4534ae9b1c5fb2e8e6573c5c apparently broke suspend for all raid(1?) multi-core systems.
In another attempt to further isolate the system parameters that trigger the issue, I set up a couple of minimal systems using various combinations of dmcrypt and raid1. As it turned out, having raid1 enabled is sufficient for triggering the issue, so commit e22bee782b3b00b d4534ae9b1c5fb2 e8e6573c5c apparently broke suspend for all raid(1?) multi-core systems.