Subj : Re: Windows Suspend/ResumeThread API equivalent for Linux or POSIX?
To   : comp.programming.threads
From : Oliver S.
Date : Thu May 12 2005 02:54 am

>> ... (esspecially when multiple worker-threads share this flag on
>> a SMP-system and need to MESI -broadcast for a newer version of
>> the cache-line containing that flag to all CPUs) ...

> Umm, no, it would stay shared until it was modified.

Oh, my fault; you're right !


>> Don't you think an API like SuspendThread / ResumeThread
>> is much smarter in that case ?

> No, I don't. In fact, it's a grossly ugly premature optimization.

That's your personal view, but _for_this_special_case_ this "opti-
mization" is ok under some circumstances. Do you really think that
polluting the code otherwise unrelated to threading-issues to check
a flag is less ugly ?

> And if you suspend the thread while it holds the 'malloc' mutex,
> you're screwed.

I've written a rendering-core of a PostScript-interpreter and this
rendering-core can be distributed among a number of processors in a
SMP-system. And the worker-threads of this core share a highly opti-
mized common memory-allocator for every device-oject. And if I sus-
pend all worker-threads attached to every device-object and using
the same memory-pool-object, this wouldn't cause any side-effects;
and there isn't any magic in taking care for this issue when wri-
ting code for worker-threads. Of course there could be cases where
you aren't able to design the worker-threads according to that rule
because you're forced to use a library that baffles that approach.

>> And as suspending an resuming a thread can be considered as a
>> longer interval of suspension through preemption, such an API
>> could be provided by an operating-system without a significant
>> cost in code-size or growth in complexity of the OS.

> It is nothing like pre-emption, because with pre-emption, the
> thread will ultimately be rescheduled with no action from user
> code, so deadlock is not possible.

Of course this is possibe, but you misunderstood me. I simply wanted
to say that the OS-code for SuspendThread / ResumeThread use the same
code for suspending and resuming the thread which the scheduler uses.

.