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Groups > comp.sys.acorn.programmer > #1498
| From | Martin Wuerthner <spamtrap@mw-software.com> |
|---|---|
| Newsgroups | comp.sys.acorn.programmer |
| Subject | Re: OS_GBPB 12 in a Wimp task |
| Date | 2012-03-12 16:44 +0100 |
| Organization | MW Software |
| Message-ID | <bf895b6f52.martin@bach.planiverse.com> (permalink) |
| References | (6 earlier) <8299b36e52.Matthew@sinenomine.freeserve.co.uk> <almarsoft.6587021169203963779@news.orange.fr> <d670e66e52.wra1th@wra1th.plus.com> <almarsoft.8991976711320644983@news.orange.fr> <5fa2466f52.wra1th@wra1th.plus.com> |
In message <5fa2466f52.wra1th@wra1th.plus.com>
Gavin Wraith <gavin@wra1th.plus.com> wrote:
> In message <almarsoft.8991976711320644983@news.orange.fr>
> Rick Murray <heyrickmail-usenet@yahoo.co.uk> wrote:
>> Your app does a partial OS_GBPB to read an epic list of files (say,
>> the contents of a well stocked manga scanlation folder). For speed,
>> it'll do them twenty at a time.
>>
>> What happens if:
>> 1. Something else does an OS_GBPB, especially if within the same
>> directory structure?
>>
>> 2. The list of files *changes* in between polls, like you're counting
>> and moving the same stuff at the same time?
>>
>> While you as an application need to keep track of your own state, the
>> filesystem hands you a value in R4 of OS_GBPB 12 which may not be
>> valid at some indeterminate time in the future...
> I do not think we are in disagreement. I cannot see how any filing
> operations (or access to any mutable shared resource) can be
> multitasked unless there is some locking semaphore. I do not know what
> RISC OS does about this. Can anybody more knowledgeable give a quick answer?
You are fully right, filing system operations can only be safely
multitasked with semaphores, but RISC OS does not have any locking
mechanism. It could not because all operations are blocking, so an
operation has to succeed or fail immediately, it cannot wait.
The simple conclusion is that multitasked filing system operations are
not safe in a transactional sense. But then, if you wanted that, you
would not use a RISC OS filing system.
--
Martin
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Martin Wuerthner MW Software http://www.mw-software.com/
RISC OS Software for Design, Printing and Publishing
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OS_GBPB 12 in a Wimp task Christopher Bazley <cs99cjb@gmail.com> - 2012-03-06 14:33 -0800
Re: OS_GBPB 12 in a Wimp task jeff <jeffrey.a.doggett@gmail.com> - 2012-03-07 00:02 -0800
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-08 22:33 +0000
Re: OS_GBPB 12 in a Wimp task Christopher Bazley <cs99cjb@gmail.com> - 2012-03-10 10:22 -0800
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-10 21:04 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-10 23:11 +0100
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-11 09:10 +0000
Re: OS_GBPB 12 in a Wimp task Chris Johnson <chrisjohnson+news@spamcop.net> - 2012-03-11 10:41 +0000
Re: OS_GBPB 12 in a Wimp task Steve Fryatt <news@stevefryatt.org.uk> - 2012-03-11 11:06 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-11 17:56 +0100
Re: OS_GBPB 12 in a Wimp task Gavin Wraith <gavin@wra1th.plus.com> - 2012-03-11 18:25 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-12 00:33 +0100
Re: OS_GBPB 12 in a Wimp task Gavin Wraith <gavin@wra1th.plus.com> - 2012-03-12 11:56 +0000
Re: OS_GBPB 12 in a Wimp task Martin Wuerthner <spamtrap@mw-software.com> - 2012-03-12 16:44 +0100
Re: OS_GBPB 12 in a Wimp task druck <news@druck.org.uk> - 2012-03-12 20:57 +0000
Re: OS_GBPB 12 in a Wimp task Martin Wuerthner <spamtrap@mw-software.com> - 2012-03-12 22:26 +0100
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-13 17:50 +0100
Re: OS_GBPB 12 in a Wimp task jgharston <jgh@arcade.demon.co.uk> - 2012-03-13 10:15 -0700
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-13 07:34 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-14 06:00 +0100
Re: OS_GBPB 12 in a Wimp task Christopher Bazley <cs99cjb@gmail.com> - 2012-03-15 02:40 -0700
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-15 14:55 +0100
Re: OS_GBPB 12 in a Wimp task "Ste (news)" <steve@revi11.plus.com> - 2012-03-15 14:46 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-15 18:44 +0100
Re: OS_GBPB 12 in a Wimp task Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2012-03-15 19:44 +0000
Re: OS_GBPB 12 in a Wimp task Alan Adams <alan@adamshome.org.uk> - 2012-03-15 20:36 +0000
Re: OS_GBPB 12 in a Wimp task Chris Johnson <chrisjohnson+news@spamcop.net> - 2012-03-15 20:26 +0000
Re: OS_GBPB 12 in a Wimp task Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-03-16 06:12 +0100
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-15 20:34 +0000
Re: OS_GBPB 12 in a Wimp task Alan Adams <alan@adamshome.org.uk> - 2012-03-15 21:04 +0000
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-16 00:17 +0000
Re: OS_GBPB 12 in a Wimp task Chris Johnson <chrisjohnson+news@spamcop.net> - 2012-03-10 23:58 +0000
Re: OS_GBPB 12 in a Wimp task Chris Johnson <chrisjohnson+news@spamcop.net> - 2012-03-11 10:43 +0000
Re: OS_GBPB 12 in a Wimp task jeff <jeffrey.a.doggett@gmail.com> - 2012-03-12 03:03 -0700
Re: OS_GBPB 12 in a Wimp task Chris Johnson <chrisjohnson+news@spamcop.net> - 2012-03-12 10:44 +0000
Re: OS_GBPB 12 in a Wimp task Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-03-13 07:44 +0000
Re: OS_GBPB 12 in a Wimp task jeff <jeffrey.a.doggett@gmail.com> - 2012-03-13 03:06 -0700
Re: OS_GBPB 12 in a Wimp task druck <news@druck.org.uk> - 2012-03-07 10:08 +0000
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