Hi Simon, I'm no expert in interpreting POSIX. A casual (but careful) reading of POSIX 1003.1-2004 suggests that this isn't the intended behavior. It is implied in a few places, most notably the getpid[1] documentation, that a process has only one PID (by use of the definite article when referring to it - ie, "the process ID"). The kill function[2] operates on "a process or a group of processes". It sends a signal "to the process whose process ID is equal to pid". Combined with the previous point, this suggests there should be only one process ID which can be passed to kill to send a signal to a particular process.
It may be that POSIX is weakly worded enough that either allowing or disallowing this behavior is valid. I think that allowing it is a violation of POSIX, but I can find no single, explicit, direct statement in POSIX to back this up. There is at least one other argument to disallow this behavior even if it is not technically illegal. Consider the traditional, widespread convention of pid files. This behavior drastically reduces their utility, as it greatly increases the chance of PID collisions, a case in which it is difficult to automatically (that is, without human intervention) recognize that a pid file no longer corresponds to a running process which created it. This is the case in which I encountered the behavior - when it repeatedly caused services not to restart because they encountered a thread of another process and misinterpreted it to mean the service was already running. I hope this is convincing. If not, what kind of argument would be? [1]: http://www.opengroup.org/onlinepubs/009695399/functions/getpid.html [2]: http://www.opengroup.org/onlinepubs/009695399/functions/kill.html -- kill(2) succeeds when no process corresponds to the given PID https://bugs.launchpad.net/bugs/341239 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
