SIGKILL is not really a "special case", because signals are not equivalent, they have assigned semantics. SIGSTOP also can't be caught. The fact that other sign

SIGKILL is not really a "special case", because signals are not equivalent, they have assigned semantics. SIGSTOP also can't be caught. The fact that other signals can be caught and these can't just follows from their intended purpose. If these two signals could be caught, they wouldn't be serving their purpose, and another way of forcibly killing a process would have to be devised. Could you please elaborate how fixing all uninterruptable sleeps would break existing software? Note that I'm not talking about adding any new I/O timeouts to NFS or anything else during normal operation - only that when a process receives SIGKILL it will die immediately, as opposed to when the I/O completes. But if you're sending SIGKILL you surely want the process to die.