Re: [RFC PATCH v1 00/13] exec: add spawn templates for repeated executable startup

[Li Chen <me@linux.beauty>]

Hi Christian,

Thanks a lot for your great review!

 ---- On Thu, 28 May 2026 19:02:53 +0800  Christian Brauner <brauner@kernel.org> wrote --- 
 > On Thu, May 28, 2026 at 05:52:21PM +0800, Li Chen wrote:
 > > Hi,
 > > 
 > > This is an early RFC for an idea that is probably still rough in both the
 > > UAPI and implementation details. Sorry for the rough edges; I am sending
 > > it now to check whether this direction is worth pursuing and to get
 > > feedback on the kernel/userspace boundary.
 > 
 > The idea of having a builder api for exec isn't all that crazy. But it
 > should simply be built on top of pidfds and thus pidfs itself instead.
 > It has all the basic infrastructure in place already.

Yes, that makes a lot more sense. I was staring too hard at the "hot
executable" part and made the cache/template the API, which was probably
the wrong thing to expose. Sorry about that.

 > Any implementation
 > should also allow userspace to implement posix_spawn() on top of it.

That's so cool, and this is a really useful point. I had not thought about this as
something that could sit under posix_spawn(), but that makes the target
much clearer. It should be a generic exec/spawn builder first, and the
agent use case should just be one user of it.

 > fd = pidfd_open(0, PIDFD_EMPTY /* or better name */)
 > 
 > pidfd_config(fd, ...) // modeled similar to fsconfig()

Reusing pidfd_open() with an empty target is nice because it keeps the API close
to pidfds, but I wonder if a separate entry point such as
pidfd_spawn_open() or pidfd_create() would make the "new process
builder" case a bit more explicit? Either way, the configuration side
being fsconfig-like makes sense to me.

Thanks again for pointing me in this direction. It helps a lot.

Regards,
Li​