panic: ptrace status unexpected: got 31, wanted stopped

goroutine 4625333 [running]:
gvisor.googlesource.com/gvisor/pkg/sentry/platform/ptrace.(*thread).wait(0xc001205d10, 0x0, 0xce30)
	pkg/sentry/platform/ptrace/subprocess.go:323 +0x4b9
DIAGNOSIS:
I0415 16:19:42.094501   53445 x:0] ***************************
I0415 16:19:42.094619   53445 x:0] Args: [/syzkaller/managers/kvm-direct-overlay-host-race/current/image -root /syzkaller/managers/kvm-direct-overlay-host-race/workdir/gvisor_root -watchdog-action=panic -network=none -debug -platform=ptrace -file-access=exclusive -overlay -network=host debug -stacks ci-gvisor-kvm-direct-overlay-host-race-0]
I0415 16:19:42.094680   53445 x:0] Version release-20190304.1-116-g546a1df7d15f
I0415 16:19:42.094698   53445 x:0] PID: 53445
I0415 16:19:42.094731   53445 x:0] UID: 0, GID: 0
I0415 16:19:42.094762   53445 x:0] Configuration:
I0415 16:19:42.094777   53445 x:0] 		RootDir: /syzkaller/managers/kvm-direct-overlay-host-race/workdir/gvisor_root
I0415 16:19:42.094807   53445 x:0] 		Platform: ptrace
I0415 16:19:42.094838   53445 x:0] 		FileAccess: exclusive, overlay: true
I0415 16:19:42.094861   53445 x:0] 		Network: host, logging: false
I0415 16:19:42.096278   53445 x:0] 		Strace: false, max size: 1024, syscalls: []
I0415 16:19:42.096367   53445 x:0] ***************************
D0415 16:19:42.097257   53445 x:0] Load container "/syzkaller/managers/kvm-direct-overlay-host-race/workdir/gvisor_root" "ci-gvisor-kvm-direct-overlay-host-race-0"
D0415 16:19:42.107478   53445 x:0] Signal container "ci-gvisor-kvm-direct-overlay-host-race-0": signal 0
D0415 16:19:42.107572   53445 x:0] Signal sandbox "ci-gvisor-kvm-direct-overlay-host-race-0"
D0415 16:19:42.107612   53445 x:0] Connecting to sandbox "ci-gvisor-kvm-direct-overlay-host-race-0"
D0415 16:19:42.110554   53445 x:0] urpc: successfully marshalled 120 bytes.
I0415 16:19:42.640706   53445 x:0] Found sandbox "ci-gvisor-kvm-direct-overlay-host-race-0", PID: 8421
I0415 16:19:42.640784   53445 x:0] Retrieving sandbox stacks
D0415 16:19:42.641082   53445 x:0] Stacks sandbox "ci-gvisor-kvm-direct-overlay-host-race-0"
D0415 16:19:42.641178   53445 x:0] Connecting to sandbox "ci-gvisor-kvm-direct-overlay-host-race-0"
D0415 16:19:42.641345   53445 x:0] urpc: successfully marshalled 36 bytes.
W0415 16:19:42.729229   53445 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-kvm-direct-overlay-host-race-0" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-kvm-direct-overlay-host-race-0" stacks: urpc method "debug.Stacks" failed: connection reset by peer