[konsole] [Bug 372991] New: Terminal gets stuck on interrupting a program that is outputting, preventing further output from being shown

[Peter Wu]

https://bugs.kde.org/show_bug.cgi?id=372991

            Bug ID: 372991
           Summary: Terminal gets stuck on interrupting a program that is
                    outputting, preventing further output from being shown
           Product: konsole
           Version: master
          Platform: Archlinux Packages
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: konsole-devel at kde.org
          Reporter: peter at lekensteyn.nl
  Target Milestone: ---

Created attachment 102469
  --> https://bugs.kde.org/attachment.cgi?id=102469&action=edit
perf trace log (executing xxd, interrupt, xxd, interrupt (=hang), ls)

When interrupting a program (^C), sometimes the output in Konsole is no longer
being updated.

Steps to reproduce:
1. Open Konsole (a new window, tab, etc.)
2. Execute "xxd < /dev/urandom"
3. Press ^C after a few seconds.
4. Repeat 2-3 a few times until the output is no longer updating.

Expected results:
Terminal should always keep the output updated, showing the prompt when the
program is interrupted. Example output:

00011310: e015 2350 cb8e dba9 00f2 8b36 a030 4b6a  ..#P.......6.0Kj
00011320: 1748 a332 bb9f 07d2 dffe 0098 a236 ad69  ^C
peter at al:/tmp$ [cursor]


Actual results:
Terminal output stops updating. Example output:

000125a0: ab6d dbb7 f02f 8288 2f94 e893 1469 8190  .m.../../....i..
000125b0: 7413 52ce c39e 2843 aeb9 d423 57c3 413b  t.R...(C...#W.A;
000125c0: 3e6a 4f8d 5c88 d34f e68[cursor]

Input is still accepted and the terminal in fact still functions, except that
the output is not being updated (the cursor position does not advance).
If you execute "touch x" for example, the file "x" will be created.
The tab title is also updated (execute "sleep 10" for example).
The output is still not updated in all these cases:
* "Saving Output As..." also shows the same.
* "Clear Scrollback" removes scrollback, but that's it.
* "Clear Scrollback and Reset" wipes a lot and moves the output, but that's it.


Other details:
As developer I have this issue for some months now and it does not always
require a lot of output (it also happened when interrupting the "ninja" build
command).

Reproduction under strace failed, but "perf trace -o st.txt src/konsole" was
successful to reproduce it.

Environment details:
- Hardware: laptop (CPU i7-6700HQ, 32GB RAM).
- konsole 16.08.3-1 (Arch Linux packages)
- konsole v16.08.2-83-g378518e (built with ASAN)
- qt5-base v5.7.0-6 (also reproduced when built with ASAN)

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