Re: Speaking of Multiprocessing...

From	Rob Gaddi <rgaddi@highlandtechnology.invalid>
Newsgroups	comp.arch.embedded
Subject	Re: Speaking of Multiprocessing...
Date	2017-03-24 16:33 -0700
Organization	A noiseless patient Spider
Message-ID	<ob4a6v$t19$1@dont-email.me> (permalink)
References	(4 earlier) <ob2cck$cu5$1@dont-email.me> <0if9dc9uphm9mrvjjstp1s30ah5fdcfd4i@4ax.com> <ob3la6$hgb$1@dont-email.me> <ob4772$grc$1@dont-email.me> <ob49hb$r43$1@dont-email.me>

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On 03/24/2017 04:22 PM, rickman wrote:
> On 3/24/2017 6:42 PM, Dimiter_Popoff wrote:
>> On 24.3.2017 г. 19:36, rickman wrote:
>>> ...
>>>
>>> Why don't I want to add a bit per memory location?  If that bit happens
>>> to be free, I'd be silly to let it go to waste.
>>
>> I am not sure a bit per reservation unit will work in a multiprocessor
>> environment (it certainly will on your single core design, obviously).
>>
>> Both the reserved address (range, typically) and the reserving processor
>> will need to know who reserved what. But this is just a "gut feeling",
>> I did not think seriously about it.
>>>
>>> Again, an abbreviation I don't know.  What's a TAS?
>>
>> Test And Set, a classic 68k RMW opcoode. Read a byte (just byte size
>> allowed), adjust the Z flag (Z IIRC...) to the state of bit 7 (MSB),
>> then write the byte back with bit 7 set. While doing this the processor
>> provides some means (holds AS asserted on the 68k IIRC) such that the
>> access to the address can not be granted to another processor for the
>> entire duration of the TAS opcode.
>>
>> Looks like in your case a simple bset (again 68k lingo, bit test and
>> set, but on two separate memory accesses, potentially interruptible
>> by another bus master - not by a processor interrupt, it is a single
>> instruction) will do what you need.
>
> Not interruptible in any way, shape or form in my approach.  The read
> and write happen in the same clock cycle - one of the beauties of having
> dual port memory in an FPGA.
>

Sounds similar to the old ARM answer to the problem: SWP Rdst, Rsrc, [addr].



-- 
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order.  See above to fix.

Thread

Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-23 18:38 -0400
  Re: Speaking of Multiprocessing... Tim Wescott <seemywebsite@myfooter.really> - 2017-03-23 18:19 -0500
    Re: Speaking of Multiprocessing... Don Y <blockedofcourse@foo.invalid> - 2017-03-23 16:26 -0700
      Re: Speaking of Multiprocessing... Tim Wescott <seemywebsite@myfooter.really> - 2017-03-23 18:47 -0500
        Re: Speaking of Multiprocessing... Don Y <blockedofcourse@foo.invalid> - 2017-03-23 17:49 -0700
          Re: Speaking of Multiprocessing... upsidedown@downunder.com - 2017-03-24 09:48 +0200
            Re: Speaking of Multiprocessing... Don Y <blockedofcourse@foo.invalid> - 2017-03-24 01:22 -0700
        Re: Speaking of Multiprocessing... Clifford Heath <no.spam@please.net> - 2017-03-24 21:04 +1100
          Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-24 22:01 -0500
            Re: Speaking of Multiprocessing... Clifford Heath <no.spam@please.net> - 2017-03-25 18:49 +1100
    Re: Speaking of Multiprocessing... Grant Edwards <invalid@invalid.invalid> - 2017-03-24 14:36 +0000
  Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-23 22:43 -0500
    Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 01:05 -0400
      Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-24 00:37 -0500
        Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 01:58 -0400
          Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-24 02:07 -0500
            Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 13:36 -0400
              Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-24 19:06 +0100
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 14:12 -0400
                Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-25 01:48 +0100
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 22:10 -0400
                Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-25 15:25 +0100
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-25 15:27 -0400
                Re: Speaking of Multiprocessing... upsidedown@downunder.com - 2017-03-25 22:43 +0200
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-25 17:06 -0400
                Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-26 17:28 +0200
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-26 13:27 -0400
              Re: Speaking of Multiprocessing... Dimiter_Popoff <dp@tgi-sci.com> - 2017-03-25 00:42 +0200
                Re: Speaking of Multiprocessing... rickman <gnuarm@gmail.com> - 2017-03-24 19:22 -0400
                Re: Speaking of Multiprocessing... Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2017-03-24 16:33 -0700
                Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-24 22:47 -0500
                Re: Speaking of Multiprocessing... Dimiter_Popoff <dp@tgi-sci.com> - 2017-03-25 12:40 +0200
                Re: Speaking of Multiprocessing... Robert Wessel <robertwessel2@yahoo.com> - 2017-03-26 00:42 -0500
  Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-24 09:17 +0100
    Re: Speaking of Multiprocessing... Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-03-24 09:28 +0000
      Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-24 11:19 +0100
        Re: Speaking of Multiprocessing... Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-03-24 11:06 +0000
          Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-24 12:21 +0100
        Re: Speaking of Multiprocessing... Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-03-24 16:09 +0000
          Re: Speaking of Multiprocessing... David Brown <david.brown@hesbynett.no> - 2017-03-24 17:33 +0100
            Re: Speaking of Multiprocessing... Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-03-24 17:52 +0000

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