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From: mwoehlke <mwoehlke AT tibco DOT com>
Subject:  Re: rsync over ssh hang issue understood
Date:  Fri, 30 Jun 2006 16:37:59 -0500
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Darryl Miles wrote:
> mwoehlke wrote:
>> Darryl Miles wrote:
>> [snip]
>>>  * The outstanding byte count needs to be protected by a mutex.
>>
>> Are you familiar with the Interlocked* family of functions? Depending 
>> on what exactly you need to do with the value, a mutex may be 
>> unnecessary.
> 
> Do these function perform buslock prefixed increment/add with memory 
> operand.   As per Linux kernel /usr/src/linux/include/asm-i386/atomic.h. 
>  Its an atomic add operation that would be needed, but I dont think that 
> will be the only thing that will need intra-thread protection.  The 
> close() case flag setting might need to be involved too as well as other 
> things, like we need serialization.

Um... probably? Did you try looking at them? There is an 
InterlockedExchangeAdd (I think that's the right name... anyway, you 
feed it a pointer and a constant, and you get back the previous value). 
At any rate, anything Linux can do in assembly, Windows can also do, 
also in assembly, with it's own __asm keyword. The syntax is a little 
different, but it's there, and for something as speed-sensitive as I 
would guess pipes are, this sort of optimization is probably a Good Thing.

Mostly, there is an Interlocked function that will save you from inline 
assembly of most assembly instructions that accept the 'lock' prefix.

Of course, if it can't be done without a mutex in assembly, then it 
can't be done without a mutex, and you remain the person (as opposed to 
me) that knows the answer to that question.

-- 
Matthew
Do not expose to hippos. Doing so may void your warranty.


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