Re: Synchronization primitives in UML (was: Re: [uml-devel] Re: [patch 09/20] uml: use SIG_IGN for empty sighandler)

[Jeff Dike <jdike@addtoit.com>]

blaisorblade_spam@yahoo.it said:
> I also understand now what all this is for. When I have time for this,
> I'll at  least copy and paste your mail into a comment, with any
> needed adjustment.

That would be a good idea.

> For the semaphore issue, I have some ideas (like using futexes) which
> need to  be developed a bit:

> 1) I want to create a semaphore API in os_*. 
> 2) It will be able to use socketpairs. 
> 3) It will be able to use futexes, if they are
> non-persistant and usable  without too much issues (the same way we
> are going to support Async I/O). 
> 4) It will be used first by the code
> which could really benefit from the  performance increase.
> 5) It won't
> use persistant objects.

This all sounds good, although there are simplicity benefits to just using
one underlying mechanism, as long as there are no overriding disadvantages
to it.

> Any comment on these issues? Also, apart TT context switching, is
> there any  other performance-sensitive use of semaphores, which would
> benefit from using  futexes? 

Offhand, I think context switching is the most sensitive one.

> Yes, semget and friends are uglier.
> But don't think that the current nested code is simple to read - three
>  semaphores at a time, without a clear name, are not the clearer code
> on the  world. 

What nested code are you talking about?

				Jeff



-------------------------------------------------------
This SF.Net email is sponsored by:
Sybase ASE Linux Express Edition - download now for FREE
LinuxWorld Reader's Choice Award Winner for best database on Linux.
http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel