[Asterisk-Dev] Re: [Asterisk-cvs] asterisk/include/asterisk module.h, 1.18, 1.19

[Slav Klenov]

Well, it sounds reasonable. I just wanted to be sure about this.

Thanks for the reply

Slav


Kevin P. Fleming wrote:

> Slav Klenov wrote:
>
>> Is it guaranteed that the res = localusecnt assignement, without 
>> holding a lock,
>> can be done safely, without any possibility of damaging res? I'm not 
>> sure if this
>> can be considered as an atomic operation.
>
>
> What does 'damaging res mean' in this context?
>
> On all modern platforms (i.e. anything with a word size of 32 bits or 
> larger), as long as the int variables involved are aligned on their 
> natural boundaries (not in a 'packed' structure), then reading or 
> writing (but _NOT_ read/modify/write) of them is always an atomic 
> operation. There is no possibility for part of the int to be written 
> and then the remainder written later.
>
> In this code, 'res' does not need to be protected, only the read from 
> 'usecnt', since 'res' is not a shared variable.
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