On Wed, Oct 23, 2024 at 08:18:35AM GMT, Lorenzo Stoakes wrote:

On Tue, Oct 22, 2024 at 05:53:00PM -0700, Shakeel Butt wrote:

quoted

On Thu, Oct 17, 2024 at 10:05:50PM GMT, Lorenzo Stoakes wrote:

quoted

It is useful to be able to utilise the pidfd mechanism to reference the
current thread or process (from a userland point of view - thread group
leader from the kernel's point of view).

Therefore introduce PIDFD_SELF_THREAD to refer to the current thread, and
PIDFD_SELF_THREAD_GROUP to refer to the current thread group leader.

For convenience and to avoid confusion from userland's perspective we alias
these:

* PIDFD_SELF is an alias for PIDFD_SELF_THREAD - This is nearly always what
  the user will want to use, as they would find it surprising if for
  instance fd's were unshared()'d and they wanted to invoke pidfd_getfd()
  and that failed.

* PIDFD_SELF_PROCESS is an alias for PIDFD_SELF_THREAD_GROUP - Most users
  have no concept of thread groups or what a thread group leader is, and
  from userland's perspective and nomenclature this is what userland
  considers to be a process.

Should users use PIDFD_SELF_PROCESS in process_madvise() for self
madvise() (once the support is added)?

You can use either it will make no difference as both will get you to
current->mm which has to be shared. So I'd go with PIDFD_SELF for brevity
:)

This series and the prerequisites I already added to process_madvise()
already provide support so with this in you can just use this for that.

Thanks a lot, this is awesome. Is the plan for this series to go through
mm-tree or through Christian?