https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122056
Bug ID: 122056
Summary: "raised TASKING_ERROR :
System.Tasking.Stages.Activate_Tasks: Failure during
activation" when online CPUs are not contiguous
Product: gcc
Version: 14.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ada
Assignee: unassigned at gcc dot gnu.org
Reporter: simon.marchi at polymtl dot ca
CC: dkm at gcc dot gnu.org
Target Milestone: ---
When trying to run this program [1] from the GDB testsuite, I get:
```
$ testsuite/outputs/gdb.ada/tasks/foo
raised TASKING_ERROR : System.Tasking.Stages.Activate_Tasks: Failure during
activation
```
I traced the problem to this code, that sets the affinity of the thread, based
on the number of CPUs.
https://github.com/gcc-mirror/gcc/blob/0088e4a419eb5cc3563a8b4b90fe71f0e33a9a84/gcc/ada/libgnarl/s-taprop__linux.adb#L995-L1020
My machine (a CI worker container started using "incus") has this special CPU
configuration:
$ nproc
8
$ cat /sys/devices/system/cpu/online
12,16,38,52,87,90,96,139
Because it sees 8 CPUs, the gcc code above creates a CPU set with bits 0-7 set.
That CPU set is passed to pthread_create, which fails with EINVAL. I presume,
because the CPU set is disjoint from the CPU numbers online on the machine. I
suppose that the CPU set should instead have bits 12,16,38,52,87,90,96,139 set
instead. Or maybe we could also not set the affinity explicitly, if the goal
is to run on all available CPUs? I don't really know, I don't know this code.
Here are some instructions to reproduce, assuming a Ubuntu 24.04 host:
$ sudo apt install incus
$ sudo usermod -aG incus-admin smarchi # Replace smarchi with correct user
$ newgrp incus-admin
$ incus admin init --minimal
$ incus launch images:debian/13 mycontainer
$ incus exec mycontainer -- bash
You should now be at the prompt in the container
root@mycontainer:~# apt update && apt install gnat wget
root@mycontainer:~# wget
https://gitlab.com/gnutools/binutils-gdb/-/raw/5b582f86bd7a6ece68f4a979c40faeffde9eec5e/gdb/testsuite/gdb.ada/tasks/foo.adb
...
root@mycontainer:~# gnatmake foo.adb
x86_64-linux-gnu-gcc-14 -c foo.adb
x86_64-linux-gnu-gnatbind-14 -x foo.ali
x86_64-linux-gnu-gnatlink-14 foo.ali
root@mycontainer:~# ./foo
The above ./foo is expected to work (produce no output, exit with 0). If you
then modify the CPUs seen by the container, like so:
$ incus config set mycontainer limits.cpu=6,8
Then in the container, you see:
root@mycontainer:~# cat /sys/devices/system/cpu/online
6,8
root@mycontainer:~# ./foo
raised TASKING_ERROR : System.Tasking.Stages.Activate_Tasks: Failure during
activation
[1]
https://gitlab.com/gnutools/binutils-gdb/-/raw/5b582f86bd7a6ece68f4a979c40faeffde9eec5e/gdb/testsuite/gdb.ada/tasks/foo.adb
