[Info-vax] LLVM, volatile and async VMS I/O and system calls

[chris]

On 09/25/21 04:42, Simon Clubley wrote:
> On 2021-09-24, chris<chris-nospam at tridac.net>  wrote:
>> On 09/24/21 19:36, Simon Clubley wrote:
>>> You therefore have to force a re-read of the buffer when you later go
>>> looking at it so the compiler doesn't think it can reuse an existing
>>> (and now stale) value.
>>
>> All i'm saying is, read the C standard docs on the use of the volatile
>> keyword for more info, or do you think you know better ?...
>>
>
> How do you otherwise _guarantee_ that the Linux application program
> is seeing the latest data that the Linux kernel might have written
> into the buffer behind the scenes since the program last looked at
> the buffer ?
>
> Simon.
>

Most kernels have system calls to deal with that sort of thing, to 
create and manage locks on shared resources and to ensure mutual
exclusion. The key thing is that that is a high level thing, whereas
things like volatile are a compile time mechanism. If you like,
the low level support foundation for high level lock mechanisms.

Others may have a better explanation of all this...

Chris