A partir da página man do ps, o campo status lhe dirá se um thread está na fila de execução (use a opção 'L' para ver os threads) -
D uninterruptible sleep (usually IO)
R running or runnable (on run queue)
S interruptible sleep (waiting for an event to complete)
T stopped by job control signal
t stopped by debugger during the tracing
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z defunct ("zombie") process, terminated but not reaped by its parent