Why doesn't kill work?
deron.meranda at gmail.com
Fri Jan 28 03:14:59 UTC 2005
On Thu, 27 Jan 2005 21:04:16 -0500, David Liguori <liguorid at albany.edu> wrote:
> In another thread a user having problems with yum killed it. I am
> curious how he accomplished that. When I run yum (or any other command,
> for that matter), it stalls, and I stop it with ctrl-z, the following
> As you see, the kill command produces no output here, but if I make up a
> pid at random it complains no such pid exists.
This is not a bug, this how it is supposed to work.
When you use control-Z from the shell to push a process to the
background, the process is also stopped (until you later use the
shell's fg or bg command). When a process is in a stopped state
any signals are queued up for it (with a few exceptions such as the
SIGKILL (-9) signal).
This could be seen by running:
near the end you'll see a line like:
Since the default signal that kill(1) sends is a SIGTERM, and
SIGTERM is 15 (in file /usr/include/bits/signum.h) and the
15th bit starting from 1 is 0x4000, you'll see that the signal
is still "pending".
Only when the process is re-awoken will the signal actually
be delivered. And it will only have it's effect when delivered.
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