[coop] Make sure suspend_count is positive in suspend request states

* Fix bug in pulse transition - the suspend count was lost and incorrectly
  swapped to 0.
* finish_async_suspend transition - add assertions that the suspend count is
  positive. Try to catch incorrect states sooner.

Fixes mono#12235

mono/utils/mono-threads-state-machine.c

@@ -487,7 +487,7 @@ mono_threads_transition_request_pulse (MonoThreadInfo* info)
 	case STATE_BLOCKING_ASYNC_SUSPENDED:
 		if (!(suspend_count == 1))
 			mono_fatal_with_history ("suspend_count = %d, but should be == 1", suspend_count);
-		if (mono_atomic_cas_i32 (&info->thread_state, STATE_BLOCKING_SUSPEND_REQUESTED, raw_state) != raw_state)
+		if (mono_atomic_cas_i32 (&info->thread_state, build_thread_state (STATE_BLOCKING_SUSPEND_REQUESTED, suspend_count), raw_state) != raw_state)
 			goto retry_state_change;
 		trace_state_change ("PULSE", info, raw_state, STATE_BLOCKING_SUSPEND_REQUESTED, -1);
 		return PulseInitAsyncPulse; // Pulse worked and caller must do async pulse, thread pulses in BLOCKING
@@ -536,11 +536,15 @@ mono_threads_transition_finish_async_suspend (MonoThreadInfo* info)
 		return FALSE; //let self suspend wait
 
 	case STATE_ASYNC_SUSPEND_REQUESTED:
+		if (!(suspend_count > 0))
+			mono_fatal_with_history ("suspend_count = %d, but should be > 0", suspend_count);
 		if (mono_atomic_cas_i32 (&info->thread_state, build_thread_state (STATE_ASYNC_SUSPENDED, suspend_count), raw_state) != raw_state)
 			goto retry_state_change;
 		trace_state_change_sigsafe ("FINISH_ASYNC_SUSPEND", info, raw_state, STATE_ASYNC_SUSPENDED, 0, "");
 		return TRUE; //Async suspend worked, now wait for resume
 	case STATE_BLOCKING_SUSPEND_REQUESTED:
+		if (!(suspend_count > 0))
+			mono_fatal_with_history ("suspend_count = %d, but should be > 0", suspend_count);
 		if (mono_atomic_cas_i32 (&info->thread_state, build_thread_state (STATE_BLOCKING_ASYNC_SUSPENDED, suspend_count), raw_state) != raw_state)
 			goto retry_state_change;
 		trace_state_change_sigsafe ("FINISH_ASYNC_SUSPEND", info, raw_state, STATE_BLOCKING_ASYNC_SUSPENDED, 0, "");