On Thu, Nov 21, 2024 at 07:33:54AM -0700, Tycho Andersen wrote:

On Wed, Nov 20, 2024 at 10:06:27AM +0100, Christian Brauner wrote:

quoted

On Tue, Nov 05, 2024 at 11:10:24AM +0800, Yun Zhou wrote:

quoted

It is necessary to have a different pid_max in different containers.
For example, multiple containers are running on a host, one of which
is Android, and its 32 bit bionic libc only accepts pid <= 65535. So
it requires the global pid_max <= 65535. This will cause configuration
conflicts with other containers and also limit the maximum number of
tasks for the entire system.

Signed-off-by: Yun Zhou <redacted>
---

Fwiw, I've done a patch like this years ago and then Alex revived it in
[1] including selftests! There's downsides to consider:

[1]: https://lore.kernel.org/lkml/20240222160915.315255-1-aleksandr.mikhalitsyn@canonical.com (local)

Thanks, looks like this patch has the same oddity.

For me it's enough to just walk up the tree when changing pid_max. It
seems unlikely that applications will create a sub pidns and then lower
the max in their own pid_max. Famous last words and all that.

I think we should revive Alex series. Not just because it has selftests
but afaict the implementation is a bit more robust.