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Groups > comp.arch.embedded > #12710
| From | Don Y <this@isnotme.com> |
|---|---|
| Newsgroups | comp.arch.embedded, comp.realtime |
| Subject | Re: Resource revocation |
| Date | 2013-07-25 15:00 -0700 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <kss75t$dgh$1@speranza.aioe.org> (permalink) |
| References | <ksrtvv$kmp$1@speranza.aioe.org> <7xehame7ut.fsf@ruckus.brouhaha.com> |
Cross-posted to 2 groups.
Hi Paul,
On 7/25/2013 12:51 PM, Paul Rubin wrote:
> Don Y <this@isnotme.com> writes:
>> What's the current "best practices" regarding asynchronous
>> notifications (in a multithreaded environment)?
>
> It would help if you specified the OS, the programming language, etc.
Nothing that you would be familiar with. I don't see how reliance on
a particular language keyword or OS hook would matter when considering
the way in which this *functionality* is availed to the developer.
I.e., do you require the developer to *poll* for the asynchronous
revocation of the resource? Do you kill the consuming thread? Do
you let him think he still has the resource and force him to *verify*
this "at the end"? Do you trap when he accesses it after it has
been revoked (how to notify of the trap?!) etc. (see below)
Assume support for threads. This implies a means by which they can
intercommunicate. And, that more than one "execution context" can
coexist. The question is, how do you *divert* execution to a
"different thread" (or subthread) based on some developer defined
constraint (that some other piece of code in the system is implementing)
>> Presently, I use signals to notify the consumer
>
> Ugh!!!
The beauty of signals is they have a history (so those of us who know
how to use them properly aren't wondering how they work or what their
pitfalls are). And, they offer a plethora of different mechanisms
by which the developer can *handle* the signal (including deferring it
*or* ignoring it!).
The biggest problem is for folks who forget to code for the
possibilities that the signals are meant to guard against.
E.g., akin to folks not knowing how to implement atomic operations,
forgetting that malloc() can return NULL (or that the region returned
can be LARGER than that requested), etc.
But, there are noticeable differences (and attendant risk) with each
of the following *different* "stylistic" approaches to the problem:
-----------
handle = await_resource(resource_required) // block until available
... // use resource
result=release_resource(handle) // formally relinquish it
if (result == you_didnt_STILL_own_it)
// resource was revoked some time while I thought I owned it
-----------
handle = await_resource(resource_required)
spawn(use_resource) // spawn a thread to do the actual work
await_release(handle)
if (flag_from_thread == my_child_released_it)
// success
else
// someone revoked it!
-----------
do {
result = attempt_resource(resource_required) // try to acquire
if (result == sorry_charlie)
// do something while waiting for resource -- or spin
else
// stop any thumb twiddling you may have started
while (result == sorry_charlie)
while (I_still_own_resource) {
// use the resource
}
if (I_finished_correctly)
release_resource
// success
else
// I must have lost resource somewhere along the line
-----------
register_handler(resource_revoked) // asynchronous handler
handle = await_resource(resource_required) // block until available
... // use resource
if (handler_was_invoked)
// did not finish as planned
else
result=release_resource(handle) // formally relinquish it
-----------
or, even a case where the handler unceremoniously/asynchronously
terminates the consumer thread! (i.e., some *other* thread can
simply monitor to see if that thread has finished its task!)
Do you err on the side of giving the developer as much *rope* as
he wants ("Now, this is how you tie a hangman's knot...") or do
you force him to handle these sorts of things in a predefined
manner -- and adapt his *problem* to your "solution"?
In the latter case, you presumably can attest to your "solution"
being *safer* than other options (however you define safe).
>> Is there a new "safer" way of implementing these types of
>> notifications?
>
> You might find this interesting:
>
> http://jlouisramblings.blogspot.com/2012/08/getting-25-megalines-of-code-to-behave.html
I didn't see anything in there germane to my question. Did I miss
something? As to "how to build robust systems", most of that is old
news...
--don
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Resource revocation Don Y <this@isnotme.com> - 2013-07-25 12:23 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 12:51 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 15:00 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 19:38 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 22:12 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 23:37 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 01:13 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 02:48 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 04:19 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 09:46 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 10:21 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:30 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 11:56 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 20:08 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 13:11 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 12:31 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 11:08 -0700
Re: Resource revocation Rob Gaddi <rgaddi@technologyhighland.invalid> - 2013-07-29 09:16 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 10:22 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 11:22 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 08:56 -0700
Re: Resource revocation Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-07-26 19:25 +0200
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 10:51 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:21 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 11:50 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:42 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:43 -0700
Does the Buddha have a real time nature? ;) (was Resource revocation) Roberto Waltman <usenet@rwaltman.com> - 2013-07-26 17:06 -0400
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Don Y <this@isnotme.com> - 2013-07-26 17:12 -0700
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 09:44 +0100
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 09:45 +0100
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Don Y <this@isnotme.com> - 2013-07-27 12:28 -0700
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-07-27 14:11 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:40 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 21:29 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 13:52 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 22:55 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 17:22 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 10:02 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 09:29 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 18:20 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 12:48 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 22:57 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:18 -0700
Re: Resource revocation Roberto Waltman <usenet@rwaltman.com> - 2013-07-31 16:33 -0400
Re: Resource revocation upsidedown@downunder.com - 2013-07-27 22:53 +0300
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 22:42 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:41 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:49 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-28 08:39 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 23:11 -0700
Re: Resource revocation Roberto Waltman <usenet@rwaltman.com> - 2013-07-31 16:15 -0400
Re: Resource revocation upsidedown@downunder.com - 2013-08-01 00:13 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:16 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:05 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:37 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:38 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 16:08 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-28 01:16 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 18:43 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-28 09:01 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:21 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:07 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:00 -0700
Re: Resource revocation stephenXXX@mpeforth.com (Stephen Pelc) - 2013-07-27 16:49 +0000
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-28 18:31 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-28 15:51 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-28 20:12 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-28 18:35 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-29 00:10 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 00:23 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 01:05 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 12:07 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 01:11 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 15:20 -0700
Re: Resource revocation Rob Gaddi <rgaddi@technologyhighland.invalid> - 2013-07-29 15:42 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 16:41 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 08:51 +0300
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 09:09 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 01:30 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 10:04 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 02:55 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 07:12 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 16:59 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 13:17 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 10:12 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 18:48 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 20:18 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-31 09:27 +0300
Re: Resource revocation [long] Don Y <this@isnotme.com> - 2013-07-31 00:47 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 02:50 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 13:22 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 07:24 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 01:17 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 19:28 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-29 11:40 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 11:44 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-29 20:56 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 13:16 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-30 00:08 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 23:41 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-31 00:58 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-31 10:18 -0700
Re: Resource revocation George Neuner <gneuner2@comcast.net> - 2013-08-02 06:19 -0400
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-08-03 02:26 -0400
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-28 19:31 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 00:44 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-25 22:42 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 22:12 -0700
Re: Resource revocation "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2013-07-31 13:41 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 07:51 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 08:07 -0700
Re: Resource revocation Anders.Montonen@kapsi.spam.stop.fi.invalid - 2013-07-31 15:55 +0000
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 10:18 -0700
Re: Resource revocation "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2013-08-01 14:42 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-08-01 14:34 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-08-02 09:08 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-08-02 07:26 -0700
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