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Re: "volatile" on variables and current processors

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On 20/08/2019 23:18, Scott Lurndal wrote:
> On ARM, the behavior will depend on the memory type.  It should work fine
> when accessing device memory (e.g. device command/status registers, PCIe
> ECAM space, etc).
> 
I've already checked and passed a bunch of those.

> For Normal, Sharable, Cacheable memory the weak (relative to x86) memory
> model will cause problems even if you qualify your accesses with the volatile
> qualifier (in a highly out-of-order pipeline, other accesses may pass the
> volatile access or vice versa, so you need a load/store with ordering
> semantics).

This is the kind of thing I need. Looks like I should worry about the 
code - it's a 3rd party lump, and it was written in C without atomics.

I'll speak to the people who pulled it in next time I'm in their country.

Thanks Paavo, Chris & David.

Andy
-- 
BTW the first machine I ever worked on professionally didn't do cache 
snooping. Cache coherency was a manual process. Which meant that 2 
processors were more than twice as fast as one on some workloads!

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"volatile" on variables and current processors Vir Campestris <vir.campestris@invalid.invalid> - 2019-08-19 21:56 +0100
  Re: "volatile" on variables and current processors red floyd <dont.bother@its.invalid> - 2019-08-19 15:20 -0700
    Re: "volatile" on variables and current processors red floyd <dont.bother@its.invalid> - 2019-08-19 15:21 -0700
      Re: "volatile" on variables and current processors "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-08-19 16:37 -0700
        Re: "volatile" on variables and current processors Vir Campestris <vir.campestris@invalid.invalid> - 2019-08-20 21:58 +0100
          Re: "volatile" on variables and current processors scott@slp53.sl.home (Scott Lurndal) - 2019-08-20 22:18 +0000
            Re: "volatile" on variables and current processors Vir Campestris <vir.campestris@invalid.invalid> - 2019-08-22 21:39 +0100
          Re: "volatile" on variables and current processors Paavo Helde <myfirstname@osa.pri.ee> - 2019-08-21 09:02 +0300
            Re: "volatile" on variables and current processors "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-08-20 23:10 -0700
          Re: "volatile" on variables and current processors David Brown <david.brown@hesbynett.no> - 2019-08-21 08:34 +0200
            Re: "volatile" on variables and current processors Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2019-08-21 20:39 +0100
              Re: "volatile" on variables and current processors Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2019-08-21 21:02 +0100
              Re: "volatile" on variables and current processors David Brown <david.brown@hesbynett.no> - 2019-08-22 13:30 +0200
        Re: "volatile" on variables and current processors Bonita Montero <Bonita.Montero@gmail.com> - 2019-08-21 08:43 +0200
      Re: "volatile" on variables and current processors "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-20 02:22 +0200
        Re: "volatile" on variables and current processors David Brown <david.brown@hesbynett.no> - 2019-08-20 10:05 +0200
    Re: "volatile" on variables and current processors Keith Thompson <kst-u@mib.org> - 2019-08-19 17:08 -0700
  Re: "volatile" on variables and current processors Bonita Montero <Bonita.Montero@gmail.com> - 2019-08-20 06:08 +0200
  Re: "volatile" on variables and current processors David Brown <david.brown@hesbynett.no> - 2019-08-20 10:14 +0200
  Re: "volatile" on variables and current processors Juha Nieminen <nospam@thanks.invalid> - 2019-08-20 13:03 +0000
    Re: "volatile" on variables and current processors David Brown <david.brown@hesbynett.no> - 2019-08-20 16:18 +0200

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