问题
Are there any cases where an application running on linux, which has not blocked signal SIGKILL, will not get killed on firing SIGKILL signal ?
回答1:
SIGKILL cannot be blocked or ignored (SIGSTOP can't either).
A process can become unresponsive to the signal if it is blocked "inside" a system call (waiting on I/O is one example - waiting on I/O on a failed NFS filesystem that is hard-mounted without the intr option for example).
(Another side case is zombie processes, but they're not really processes at that point.)
回答2:
Yes, when the process is blocked in kernel space, e.g. reading on a blocked NFS file system, or on a device which does not respond.
回答3:
Check with ps a (or you can use other flags as well) the process state.
If a process state is
D : uninterruptible sleep (usually IO)
then you cannot kill that process.
As others mentioned, and as it is defined, this is usually caused by a stuck I/O, for example process waiting to do I/O to a disconnected NFS file system.
来源：https://stackoverflow.com/questions/8600430/cases-in-which-sigkill-will-not-work