Unexpected zero values in /proc/[pid]/stat


I’m trying to port strace’s CI builds to Travis CI’s new arm64 hardware. The arm64 builds are however returning weird content for the /proc/[pid]/stat files, used in strace’s tests.

# Under arm64 build
$ cat /proc/self/stat
966 (cat) R 136 0 0

# Under AMD64 build
$ cat /proc/self/stat
3958 (cat) R 2024 2024 2024

The three numbers after “R” should be the ppid, the process group ID, and the session ID. They should not be 0. I’ve reproduced this with simple Travis CI builds, if you want to have a look.

Is this related to the LXD runtime? Even under LXD, I’m getting the expected numbers locally.


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The process group ID = 0 issue was affected for a test case of Ruby project too.

As a result, we decide to skip the test for the arm64 environment.
As a note, in “Drone CI” arm64 environment, the process group ID works.

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