tree ee081e195b02452ef768bbb26a7154a9f1292210
parent b26ebfe12f34f372cf041c6f801fa49c3fb382c5
author Christian Brauner <christian.brauner@ubuntu.com> 1583674157 +0100
committer Christian Brauner <christian.brauner@ubuntu.com> 1583793605 +0100
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pid: make ENOMEM return value more obvious

The alloc_pid() codepath used to be simpler. With the introducation of the
ability to choose specific pids in 49cb2fc42ce4 ("fork: extend clone3() to
support setting a PID") it got more complex. It hasn't been super obvious
that ENOMEM is returned when the pid namespace init process/child subreaper
of the pid namespace has died. As can be seen from multiple attempts to
improve this see e.g. [1] and most recently [2].
We regressed returning ENOMEM in [3] and [2] restored it. Let's add a
comment on top explaining that this is historic and documented behavior and
cannot easily be changed.

[1]: 35f71bc0a09a ("fork: report pid reservation failure properly")
[2]: b26ebfe12f34 ("pid: Fix error return value in some cases")
[3]: 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>