Mutex and Atomic (was 64 bit time_t on 32 bit systems)

[Gary E. Miller]

Yo Hal!

On Thu, 19 Jan 2023 21:43:08 -0800
Hal Murray <halmurray at sonic.net> wrote:

> gem at rellim.com said:
> > Sadly, that no longer works on modern CPUs with out of order
> > execution. Unless wrapped in a mutex, or atomic, and that is now a
> > no-no.   
> 
> Do you have a good reference for that?

Many ariticle on lwn.net.

> I'd like something like a nice blog article that explains things.

Sadly work in this area has been slow and disjoint.  Following lwn.net
is the onely way I know to keep up with it.

> What is the new/wonderful way?  Even if you do something like a
> kernel call with a file handle, deep inside there I'd expect a mutex
> to make sure the right thing happens if 2 threads try to do the same
> operation at the same time.

Many techniques, RCU, Red/Black trees, etc.

> Is there a blog type page describing the TIME_BITS stuff?

Yes, the gpsd issue: 

https://gitlab.com/gpsd/gpsd/-/issues/152

Which has links to other sources.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin
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