[konsole] [Bug 372991] 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

--- Comment #11 from Peter Wu <peter at lekensteyn.nl> ---
Looks like a race condition. Reproduced in QEMU 2.8.0 with Arch Linux and
Konsole 16.12.2 with plasma-desktop 5.9.3 (and also openbox). Cannot reproduce
with just one CPU (need -smp 2 or more). Command to start QEMU:

qemu-system-x86_64 -M pc,accel=kvm -m 2G -vga qxl -net user -net
nic,model=virtio -drive if=virtio,file=plasma.qcow2 -initrd initrd.img -kernel
arch/x86/boot/bzImage -append "rw root=/dev/vda1" -smp 4

A normal user was created with autologin (agetty --autologin). In openbox
(where no background activity exists), it was necessary to run "while ls&ls;do
:;done" in a separate xterm process (which would display just the directory "x"
in the home directory on an 8GB ext4 filesystem).

Tested kernels (BAD = got hang, OK = could not reproduce hang within a few
minutes):
BAD v4.9.11
BAD v4.10.1
BAD v4.1.38
OK v3.12.70 (Note: to update display, had to switch between QEMU monitor and
back)
OK v3.18.48
OK v4.0.9 (needed "ln -s compiler-gcc5.h ../include/linux/compiler-gcc6.h" to
fix GCC6 build)
BAD v4.1.38 (yes, still bad, just to be sure)
BAD v4.1.15
OK v4.1.1 (could not reproduce)
OK v4.1.7-44-g49b85054a83d (git bisect starts)
BAD v4.1.13-91-g8d0fe5721d27
[OK v4.1.10-89-g5eb491ba5d06 (actually, this is also BAD! see below)]
BAD v4.1.12-7-g4508582e6a83
[OK v4.1.10-174-gc1d40e01ad8c (actually, this is also BAD! see below)]
BAD v4.1.11-13-g7b61554c25cb
BAD v4.1.10-195-g614ea4ea2c3f (hmm, I suspect that this commit is bad)
BAD v4.1.10-194-ga0533fb8cf60 (wait, I can still reproduce? did not expect
that, bisect probably wrong)
BAD v4.1.10-184-g0cf68c236f11
BAD v4.1.10-179-g249af812dcf3
BAD v4.1.10-174-gc1d40e01ad8c (not good, bad! Can also reproduce issue)
BAD v4.1.10-89-g5eb491ba5d06 (finally got hang after trying for 5 minutes)
OK v4.1.1 (can still not reproduce after 8 minutes)
[v4.1.10-89-g5eb491ba5d06 (can still not reproduce after 6 minutes)]
[BAD v4.1.10-194-ga0533fb8cf60 (can still reproduce after 2 minutes)]

Gave up after 2-3 hours of trying... The first known bad version is
v4.1.10-89-g5eb491ba5d06. The first *possibly* good version is
v4.1.7-44-g49b85054a83d, but a quick scan through the commits (keywords, "tty",
"console", "lock") does not yield suspicuous commits.

I think I'll just try to patch this without knowing the root cause.

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