| Summary: | missing information about threads in kill(2) man page | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | David Tonhofer <bughunt> |
| Component: | util-linux-ng | Assignee: | Karel Zak <kzak> |
| Status: | CLOSED ERRATA | QA Contact: | qe-baseos-daemons |
| Severity: | low | Docs Contact: | |
| Priority: | low | ||
| Version: | 6.3 | CC: | azelinka, ovasik, pschiffe, psklenar |
| Target Milestone: | rc | Keywords: | ManPageChange |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Enhancement | |
| Doc Text: |
Feature:
The kill(1) man page has been improved to explicitly explain interaction between kill syscall and threads.
Reason:
It wasn't obvious to users how kill(1) works with threads.
Result (if any):
|
Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2013-11-21 20:43:37 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | ||
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHBA-2013-1648.html |
Description of problem: ======================= A little question on the usage of kill(2) I have run into: I have scripts that check whether a process is alive by getting a known pidfile, then issuing a "kill -o PID" to the PID contained in that pidfile. This is a standard trick of course. However, it seems that nowadays "kill -o PID" also sends signals to threads, i.e. if there is no PID, the value is assumed to be a TID and the thread is signalled (I suppose, it probably just signals whatever is in the process table at the given ID) This does not conform to the specification. Consider /bin/kill: - An strace of kill(1) shows a call to the kill(2) syscall but: - The kill(2) manpage doesn't mention threads at all. - Indeed, there is a specially designed tgkill(2) to signal threads. - The manpage of tgkill says; "By contrast, kill(2) can only be used to send a signal to a process (i.e., thread group) as a whole, and the signal will be delivered to an arbitrary thread within that process.)" Now: Should kill(1) not check whether the pid it is given belongs to a thread or a process and, in case of a thread id, simply refuse to send a signal ("kill can only be used to send a signal to a process") Shouldn't there be a tgkill(1) ? Or else, shouldn't the manpage be changed? So either the kill(2) manpage and the tgkill(2) are wrong / need to be completed or there is an implementation problem with the kill syscall.