Created attachment 403844 [details] Backtrace Description of problem: Octave's SIGCHLD handler calls operator new, which is not async-signal-safe. This can cause the "help" command to hang if the SIGCHLD from the info subprocess arrives while octave was already in a call to operator new. Version-Release number of selected component (if applicable): octave-3.2.3-4.fc12.x86_64 How reproducible: Rarely and randomly. I haven't found any tricks to make it happen more often. Steps to Reproduce: 1. Start octave. 2. help clear Actual results: Octave hangs (see attached backtrace). Expected results: The "help" command completes.
Can you reproduce this with latest octave and/or octave-forge in either F-13 or F-12?
I just reproduced the problem with octave-3.2.4-2.fc13.x86_64 on F13. I got lucky: the hang occurred on my very first try.
(In reply to comment #2) > I just reproduced the problem with octave-3.2.4-2.fc13.x86_64 on F13. I got > lucky: the hang occurred on my very first try. Do you have octave-forge installed? If so, what version? Also any other possible third-party octave packages, also it might help to move aside your ~/.octaverc file if you have one. I can't reproduce a hang using the "help" command at all. It might be useful to report this upstream and post a link to the upstream bug on this bugzilla entry.
Created attachment 432710 [details] "rpm -qa" output (In reply to comment #3) > Do you have octave-forge installed? If so, what version? Also any other > possible third-party octave packages, I don't have octave-forge installed, and I didn't intentionally install any third-party octave packages. See the attached "rpm -qa" output. > also it might help to move aside your > ~/.octaverc file if you have one. I don't have one. > I can't reproduce a hang using the "help" > command at all. This is a timing-dependent bug. It's entirely possible that it will never present for you due to differences between your system and mine. You should still be able to trigger it by artificially forcing the proper sequence of events using gdb; I will attach a typescript demonstrating this.
Created attachment 432711 [details] Demo of forcing the bug to occur using gdb
(In reply to comment #5) > Created an attachment (id=432711) [details] > Demo of forcing the bug to occur using gdb Hmm, still can't seem to reproduce myself using those steps, but I filed the bug with upstream Octave on GNU Savannah and Cc'ed you on the bug: https://savannah.gnu.org/bugs/index.php?30477 Hopefully upstream will know more about how to tackle this.
I can reproduce it with both fedora's package and (much more "reliably") with self-compiled 3.3.51. For me it works almost 100% if I do (in 3.3.51) help junk111 (or any other non-existing entry). With existing functions it is still hit-or-miss. If I set "more off" then bug happens not as often. Dmitri.
Upstream fix: http://hg.savannah.gnu.org/hgweb/octave/rev/f359cfc6e24d
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