Bug 474115
| Summary: | command hang in ksh and cpu workload is high | ||
|---|---|---|---|
| Product: | [Fedora] Fedora EPEL | Reporter: | Michal Hlavinka <mhlavink> |
| Component: | mksh | Assignee: | Robert Scheck <redhat-bugzilla> |
| Status: | CLOSED NEXTRELEASE | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | el5 | CC: | redhat-bugzilla, tg |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | 36-2 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2008-12-02 22:08:49 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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Description
Michal Hlavinka
2008-12-02 10:25:34 UTC
my mistake, strace and ltrace are originally from pdksh, but this bug is easily reproducible with mksh Ehm, is it possible, that you're mixing up ksh and mksh? You wrote ksh above, not mksh... Here's an excerpt from the mksh(1) manual page:
Aliases
There are two types of aliases: normal command aliases and tracked
aliases. Command aliases are normally used as a short hand for a long or
often used command. The shell expands command aliases (i.e. substitutes
the alias name for its value) when it reads the first word of a command.
An expanded alias is re-processed to check for more aliases. If a command
alias ends in a space or tab, the following word is also checked for
alias expansion. The alias expansion process stops when a word that is
not an alias is found, when a quoted word is found, or when an alias word
that is currently being expanded is found.
The crucial part here is: "An expanded alias is re-processed..."
So, first and foremost, this is not a bug in the shell, but a bug
in the script.
Interestingly enough, when aliasing "ls" to "ls", simply typing "ls"
on the shell command line still works, whereas typing "i=$(ls)" hangs.
I also suspect you could get me with the last sentence quoted above,
which _seems_ to try to prevent recursion loops. But I just tested
with pdksh, the ancestor, which exhibits the same behaviour, so the
solution to this problem is probably along the lines of "don't do
that then".
I will keep this in mind but do not promise a change in behaviour.
If you have a patch for mksh ready, I will however look at it.
It does not seem to be dependent on flags like "set -o trackall",
which is the only thing besides interactivity that came to my mind.
*** Bug 474114 has been marked as a duplicate of this bug. *** (In reply to comment #2) > Ehm, is it possible, that you're mixing up ksh and mksh? You wrote ksh above, > not mksh... no, it's really mksh. I have ksh->mksh symlink (In reply to comment #3) 1) ...when a quoted word is found..., there is alias ls="ls", so it's quoted 2) it works for ls but not for `ls`, it's a bug IMO 3) even if it is shell script's bug, mksh should write error as if you try to use not_existing_command or read from not_existing_file. Eat all memory is definitely a bug. 1) ...when a quoted word is found..., there is alias ls="ls", so it's quoted It's not quoted. The double quotes are stripped by the command line parser before the "alias" builtin sees the result. 2) it works for ls but not for .s, it's a bug IMO If it happens to work for "ls" despite not being specified to work at all (the re-expansion clause), it's just lucky. If it then does not happen to work for "$(ls)", this is just being once but not twice lucky. 3) even if it is shell script's bug, mksh should write error as if you try to use not_existing_command or read from not_existing_file. Eat all memory is definitely a bug. I'd rather call it "undesired behaviour", since it's a bug in your script which merely exploits it. But, as I said, let me see if I can tend to it, okay? You're of course allowed to send in a patch *smiles* (In reply to comment #3) > .. But I just tested > with pdksh, the ancestor, which exhibits the same behaviour... Yes https://bugzilla.redhat.com/show_bug.cgi?id=473528 > I will keep this in mind but do not promise a change in behaviour. > If you have a patch for mksh ready, I will however look at it. I'm going to make patch for pdksh (once it's approved - I'm assigned to the pdksh's bug). I've just thought to let you know, there is the same bug with mksh that should be fixed. Okay, I think I got the cause of the bug. Try to replace | i=$(ls) with | i=$(ls ) and it vanishes. The source is closed to SEOF early if there is no trailing space... will fix that soonish. yes, I can confirm that Fixed upstream in commitid 10049352BD82DFF462F Thanks for reporting the problem. Feel free to take the patch and apply it to the Redhat-local pdksh version (although mksh is positioned in the market as pdksh successor, seeing that it has not been under active development since 1999 or so). (In reply to comment #10) > ... although mksh > is positioned in the market as pdksh successor, seeing that it > has not been under active development since 1999 or so Yes, I know, but it's not my decision Thanks for fast fix, Michal (In reply to comment #10) > Fixed upstream in commitid 10049352BD82DFF462F where can I find that repository? Is it http://www.mirbsd.org/cvs.cgi/src/bin/mksh/ ? Because I'm unable to connect to that server (time-out) Yes, it is, but the box is currently fscking, sorry. Once it's up and the next rsync from the master repo is done, you'll be able to access it from there. mksh-36-2.fc9 has been submitted as an update for Fedora 9. http://admin.fedoraproject.org/updates/mksh-36-2.fc9 mksh-36-2.fc10 has been submitted as an update for Fedora 10. http://admin.fedoraproject.org/updates/mksh-36-2.fc10 mksh-36-2.fc8 has been submitted as an update for Fedora 8. http://admin.fedoraproject.org/updates/mksh-36-2.fc8 Package: mksh-36-2.fc11 Tag: dist-f11 Status: complete Built by: robert Package: mksh-36-2.fc10 Tag: dist-f10-updates-candidate Status: complete Built by: robert Package: mksh-36-2.fc9 Tag: dist-f9-updates-candidate Status: complete Built by: robert Package: mksh-36-2.fc8 Tag: dist-f8-updates-candidate Status: complete Built by: robert 877 (mksh): Build on target fedora-5-epel succeeded. 878 (mksh): Build on target fedora-4-epel succeeded. mksh-36-2.fc8 has been pushed to the Fedora 8 stable repository. If problems still persist, please make note of it in this bug report. mksh-36-2.fc9 has been pushed to the Fedora 9 stable repository. If problems still persist, please make note of it in this bug report. mksh-36-2.fc10 has been pushed to the Fedora 10 stable repository. If problems still persist, please make note of it in this bug report. mksh-36b-1.fc8 has been submitted as an update for Fedora 8. http://admin.fedoraproject.org/updates/mksh-36b-1.fc8 mksh-36b-1.fc9 has been submitted as an update for Fedora 9. http://admin.fedoraproject.org/updates/mksh-36b-1.fc9 mksh-36b-1.fc10 has been submitted as an update for Fedora 10. http://admin.fedoraproject.org/updates/mksh-36b-1.fc10 mksh-36b-1.fc8 has been pushed to the Fedora 8 stable repository. If problems still persist, please make note of it in this bug report. mksh-36b-1.fc10 has been pushed to the Fedora 10 stable repository. If problems still persist, please make note of it in this bug report. mksh-36b-1.fc9 has been pushed to the Fedora 9 stable repository. If problems still persist, please make note of it in this bug report. |