Re: [patch] drivers: wait for threaded probes between initcall levels

Linus Torvalds
2006-10-28T19:47:01Z

On Sat, 28 Oct 2006, Adam J. Richter wrote:

> On Fri, 27 Oct 2006 13:42:44 -0700 (PDT), Linus Torvals wrote:
> > static struct semaphore outstanding;
> [...]
> > static void allow_parallel(int n)
> [...]
> > static void wait_for_parallel(int n)
> [...]
> > static void execute_in_parallel(int (*fn)(void *), void *arg)
>
> This interface would have problems with nesting.

You miss the point.

They _wouldn't_ be nested.

The "allow_parallel()" and "wait_for_parallel()" calls would be at some
top-level situation (ie initcalls looping).

Nobody else than the top level would _ever_ use them. Anything under that
level would just say "I want to do this in parallel" - which is just a
statement, and has no nesting issues in itself.

The whole notion of "I want to do this in parallel" is basically
non-nesting. If something is parallel, it's by definition not ordered, and
thus nesting cannot make sense. All the "ordered" stuff would be either
done without using "execute_in_parallel()" at all, or it would be ordered
_within_ one thread that is executed in parallel.

Linus