| Summary: | ksh misbehavior if login shell "( cmd & )" does nothing and no error reported | |||
|---|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Paulo Andrade <pandrade> | |
| Component: | ksh | Assignee: | Michal Hlavinka <mhlavink> | |
| Status: | CLOSED ERRATA | QA Contact: | Martin Kyral <mkyral> | |
| Severity: | medium | Docs Contact: | Milan Navratil <mnavrati> | |
| Priority: | medium | |||
| Version: | 6.6 | CC: | dkutalek, mnavrati, ovasik | |
| Target Milestone: | rc | Keywords: | Patch | |
| Target Release: | --- | |||
| Hardware: | All | |||
| OS: | All | |||
| Whiteboard: | ||||
| Fixed In Version: | ksh-20120801-32.el6 | Doc Type: | Bug Fix | |
| Doc Text: |
KornShell no longer omits a background process in a command list when forking
Due to a bug in KornShell (ksh), forking a background process in a command list could previously omit that process completely. The source code that handles forking sub-processes has been modified, and a background process in a command list is now executed as expected.
|
Story Points: | --- | |
| Clone Of: | ||||
| : | 1217237 1217238 (view as bug list) | Environment: | ||
| Last Closed: | 2016-05-11 00:45:47 UTC | Type: | Bug | |
| Regression: | --- | Mount Type: | --- | |
| Documentation: | --- | CRM: | ||
| Verified Versions: | Category: | --- | ||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | ||
| Cloudforms Team: | --- | Target Upstream Version: | ||
| Bug Depends On: | ||||
| Bug Blocks: | 1075802, 1172231, 1217237, 1217238, 1254457, 1269889 | |||
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. https://rhn.redhat.com/errata/RHBA-2016-0932.html |
To test, either have ksh as login shell, or create a test user. Then ssh localhost. Sample session: ---8<--- $ cd /tmp/alan $ cat tst.ksh #!/bin/ksh D=$(date) echo $D > /tmp/alan/tst.dat $ ls tst.ksh $ (ksh /tmp/alan/tst.ksh &) [1] 28190 $ ls tst.ksh ---8<--- This happens due to a double fork, once for "( cmd )" and then the first fork forks again due to the "&", but, just when the child branches, it receives a SIGHUP and immediately exits. I tested a quick&dirty patch, that basically reverts to rhel5 ksh behavior, and there are no regressions in the test cases. ---8<--- diff -up ksh-20120801/src/cmd/ksh93/sh/xec.c.orig ksh-20120801/src/cmd/ksh93/sh/xec.c --- ksh-20120801/src/cmd/ksh93/sh/xec.c.orig 2015-04-28 16:55:25.521818636 -0300 +++ ksh-20120801/src/cmd/ksh93/sh/xec.c 2015-04-28 16:56:34.037753565 -0300 @@ -2059,16 +2059,20 @@ int sh_exec(register const Shnode_t *t, } else if(((type=t->par.partre->tre.tretyp)&FAMP) && ((type&COMMSK)==TFORK)) { +#if 0 pid_t pid; sfsync(NIL(Sfio_t*)); while((pid=fork())< 0) _sh_fork(shp,pid,0,0); if(pid==0) { +#endif sh_exec(t->par.partre,flags); +#if 0 shp->st.trapcom[0]=0; sh_done(shp,0); } +#endif } else sh_subshell(shp,t->par.partre,flags,0); ---8<--- I also asked upstream, see http://lists.research.att.com/pipermail/ast-users/2015q2/004754.html but actually, there is a bad comment there, about crashes if running it as "( cmd ) &". Likely it was due to the way I was debugging it. Note that if one has bash as login shell, then starts, or exec ksh, or even if has ksh as login shell, and first exec ksh, it will work, because then SIGHUP will be blocked in the "orphan" process (orphan due to double fork).