Greetings... a patch I would like your comments on...

[Randall Stewart]

Ivan:

A couple of comments...

On Jan 22, 2010, at 7:33 AM, Ivan Voras wrote:

> On 01/22/10 16:10, Ed Schouten wrote:
>> * Ivan Voras<ivoras at freebsd.org>  wrote:
>>> This is a good and useful addition! I think Windows has  
>>> implemented a
>>> generalization of this (called "wait objects" or something like  
>>> that),
>>> which effectively allows a select()- (or in this case kqueue())-like
>>> syscall to wait on both file descriptors and condvars (as well as
>>> probably other MS-style objects). It's useful for multiplexing  
>>> events
>>> for dissimilar sources.
>>
>> NtWaitForSingleObject(), NtWaitForMultipleObjects(), etc. :-)
>>
>
> Yes, I was thinking about WaitForMultipleObjects() - I sometimes  
> wished I had it in FreeBSD :)
>
> I think the hackers@ side of the thread is missing the original link  
> to the patch file offered for review, so here it is:
>
> http://people.freebsd.org/~rrs/kque_umtx.patch
>
> My kqueue-fu level is too low to be really useful here but from what  
> I've read it looks like a logical and even reasonably clean way of  
> doing it.

thanks it made sense to me ;-)

>
> If I read the comment at filt_umtxattach() correctly, in the best  
> case you would need an extension to the kevent structure to add more  
> fields like data & udata (for passing values back and forth between  
> userland and kernel). I agree with this - it would be very  
> convenient for some future purposes (like file modification  
> notification) if the kernel filter could both accept and return a  
> struct of data from/to the userland.

Yeah, more arguments inside the kevent would allow me to add the  
COND_CV_WAIT* where a lock and condition are passed
in as well... But I was hesitant to add more than was already there  
since doing
so would cause ABI ripples that I did not want to face.

I plan on committing this to head if I don't get strong "you idiot you  
did it wrong" comments ;-)


R

>
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------------------------------
Randall Stewart
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