Re: [patch 05/13] syslets: core, documentation

Ingo Molnar
2007-02-27T06:28:47Z

* Randy Dunlap <randy.dunlap@oracle.com> wrote:

> > + [ Note: since the argument array is at the end of the atom, and the
> > + kernel will not touch any argument beyond the final NULL one, atoms
>
> I would s/final/first/ since one could put many (unneeded) NULL
> pointers in the argument array.

ok, fixed.

> > +Completion of asynchronous syslets is done via the 'completion ring',
> > +which is a ringbuffer of syslet atom pointers user user-space memory,
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^^^^ ^^^^ ??

fixed - it's "in user-space memory".

> > +provided by user-space as an argument to the sys_async_exec() syscall.
> > +The kernel fills in the ringbuffer starting at index 0, and user-space
> > +must clear out these pointers. Once the kernel reaches the end of
> > +the ring it wraps back to index 0. The kernel will not overwrite
> > +non-NULL pointers (but will return an error), user-space has to
> > +make sure it completes all events it asked for.
>
> Last sentence is actually 2 sentences, so (e.g.) change the comma
> to a semi-colon, xor begin the sentence with "Since".

i've changed it to ', and thus user-space has to make sure'.

> How does the kernel return an error if the ring buffer is full? Just a
> syscall negative error return code?

correct - we return a -EFAULT in that case. Should probably do something
more distinguished though?

> > + /*
> > + * Simple syslet consisting of a single atom:
> > + */
> > + init_atom(&atom, __NR_sys_write, &fd_out, &buf, &size,
> > + NULL, NULL, NULL, NULL, SYSLET_ASYNC, NULL);
>
> init_atom() (was) above. sys_async_exec(), sys_async_wait() are new
> syscalls. What are async_head_init() and async_head_exit()?

They used to initialize kernel-side stuff too, but now they only
initialize the user-space-head structure: the ring and a 'head stack
pointer'.

Ingo