just curious

[Terry Lambert]

Matthew Dillon wrote:
>     Another thing that shouldn't be missed here is that a messaging syscall
>     interface allows us to use an incremental development model for the
>     userland and kernelland threading support.  The userland can fire off
>     'asynchronous' system calls to the kernel without being any the wiser
>     as to how the kernel actually deals with them.  We could initially
>     implement an internal rfork() mechanism for the kernel to run the
>     'asynchronous' system calls.
> 
>     Userland thread library development could proceed without having to
>     wait for complete threading support in the kernel, and asynchronization
>     of individual blockable syscalls in the kernel can be worked on
>     in piecemeal and in parallel.
> 
>     That's a very big deal!  It makes me want to tackle the syscall
>     messaging next, but I'm set on doing DEV first.  Maybe I'll tackle
>     the basic syscall messaging support before I do VFS.

FWIW, this is what I originally envisioned when I first suggested
the use of an "async call gate" for implementing threads on FreeBSD,
but was sot down over legacy support issues with static binaries,
and FreeBSD ended up with a more traditional scheduler activations
implementation instead.  Then they had to go 64 bit for a lot of
system calls, and ended up implementing new system calls anyway,
only they still weren't async.  8-).

-- Terry