Package: gnuplot
Version: 4.4.0-1.1
Severity: normal
gnuplot hangs on the following small script
plot x
pause -1
set term post
if the X11 window (default terminal wxt) is killed with xkill (or the
X11 connection gets disconnected by other means ...).
"Hangs" means being unresponsive to <RETURN> (e.g. end the pause
command) or <Ctrl>-<C>. I have to use <Ctrl>-<Z> and kill %1 to
terminate the process.
The problem did not occur in 4.2.2-1.2 (wxt terminal).
The problem does not happen with the x11 terminal (only tested 4.4.0-1.1).
The problem still exists in 4.4.2 (the packaging of 4.4.0-1.1 worked
without changes for 4.4.2, too).
I also rebuilt gnuplot 4.2.2-1.2 on sid using libwxgtk2.8-dev instead of
libwxgtk2.6-dev. The problem does not appear in this configuration, so it
is not a wxgtk 2.6 vs. 2.8 issue.
Andreas
----------
Following is the original report I wanted to send until I found a much
simpler way to reproduce it. The details should still apply ...
I use gnuplot w/ default wxt terminal often on remote hosts (accessed via
ssh with X11 forwarding) inside screen (i.e. SCREEN(1)).
Whenever I loose the connection to the remote machine (e.g. moving
the notebook between home and office) while there is an X window open,
the running gnuplot command (which is not affected by the disconnect because
it is running inside screen) hangs. There is an error message about the
lost X11 connection (as expected) and the gnuplot process is no longer
responding to either <Return> or <Ctrl>-<C>. I have to <Ctrl>-<Z> it and
kill %1 to terminate it. This was working much smoother in 4.2.x where
this connection loss just worked like a closed window.
Checking with strace shows that the process is hanging doing some
futex(...)
call.
This is not neccessarily a problem in gnuplot, but could be in the WX
libraries (2.6 vs. 2.8) as well. It is not a problem in X11 libraries -
this I just verified by downgrading 4.4.0-1.1 to 4.2.2-1.2 while keeping
everything else at the same same version and upgrading later on again.
Package changes I did during the upgrade back to 4.4:
before, i.e. removed:
ii libwxbase2.6-0 2.6.3.2.2-3+lenny1 wxBase library (runtime) -
ii libwxgtk2.6-0 2.6.3.2.2-3+lenny1 wxWidgets Cross-platform C++
ii gnuplot 4.2.2-1.2 A command-line driven
ii gnuplot-nox 4.2.2-1.2 A command-line driven
ii gnuplot-x11 4.2.2-1.2 X11-terminal driver for
after, e.g. installed:
ii gnuplot 4.4.0-1.1 A command-line driven
ii gnuplot-nox 4.4.0-1.1+b1 A command-line driven
ii gnuplot-x11 4.4.0-1.1+b1 A command-line driven
ii groff 1.20.1-10 GNU troff text-formatting
The problem is easily reproducible the following way:
local$ ssh remote
remote$ screen # start screen
remote $ cat something.gnuplot
plot sin(x)
pause -1
set term png size 800,600
remote_screen$ gnuplot something.gnuplot # opens X11 window
^A^D # detach from screen
remote$ ^D # close shell, X11 window is still open
^C # terminate ssh connection (which stayed open
# because the X11 channel is still open)
local$ ssh remote
remote$ screen -x # reconnect to screen
# shows up the old terminal content, ending with
<unknown>: Fatal IO error 11 (Resource temporarily unavailable) on X
server localhost:10.0.
<RETURN> # no reaction
^C # no reaction
in separate screen windows I started strace on both threads and issued
<RETURN> and ^C again:
$ strace -p 2120
Process 2120 attached - interrupt to quit
futex(0x2752e60, FUTEX_WAIT_PRIVATE, 2, NULL) = ? ERESTARTSYS (To be
restarted)
--- SIGINT (Interrupt) @ 0 (0) ---
rt_sigaction(SIGINT, {0x4e16c0, [INT], SA_RESTORER|SA_RESTART,
0x2b23ad4891e0}, {0x4e16c0, [INT], SA_RESTORER|SA_RESTART,
0x2b23ad4891e0}, 8) = 0
rt_sigreturn(0x2) = 202
futex(0x2752e60, FUTEX_WAIT_PRIVATE, 2, NULL
$ strace -p 2121
Process 2121 attached - interrupt to quit
futex(0x2752e60, FUTEX_WAIT_PRIVATE, 2, NULL
This intensive testing and testcase generation revealed that if I remove
the third line (set term png) and any further code from my gnuplot file,
this problem does not occur.
I also tried updating to 4.4.2 (the 4.4.0-1.1 packaging worked without
changes for 4.4.2, too), but this does not fix the problem.
And we can now greatly simplify the reproduction process of this problem
to use the local machine and xkill ...
Andreas
-- System Information:
Debian Release: squeeze/sid
APT prefers stable
APT policy: (800, 'stable'), (700, 'testing'), (600, 'unstable'), (130,
'experimental')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.32-5-amd64 (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages gnuplot depends on:
ii gnuplot-nox 4.4.0-1.1+b1 A command-line driven interactive
ii gnuplot-x11 4.4.0-1.1+b1 A command-line driven interactive
gnuplot recommends no packages.
Versions of packages gnuplot suggests:
pn gnuplot-doc <none> (no description available)
-- no debconf information
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