Thank you for your thoughts.
Unfortunately, I don't think the mutex hack will work, because there is
sometimes a one-to-many relationship between the signaling thread and
the waiting threads.
Also, thanks for the heads up about the instability of CV's right now.
While we're talking, I'll mention that I've thought about submitting a
timed version of condition-wait as a suggested patch. In OpenMCL, my
application eventually frees up OS resources by letting threads expire
after 60 seconds, but there's currently no such mechanism in SBCL.
Marco Monteiro wrote:
> No, I don't think there is such thing. Maybe it is not a condition
> variable that you need. You can implement other primitives with mutex
> and condition variables, but you will still have the overhead.
> But here is a nice, inventive, and powerfull (even if a little wicked
> and bit naughty) way to do something like that. Why don't you use a
> mutex to simulate what you want? Do a SB-THREAD:MAKE-MUTEX followed by a
> SB-THREAD:GET-MUTEX. Now, the following SB-THREAD:GET-MUTEX blocks a
> thread (more or less a CONDITION-WAIT) and SB-THREAD:RELEASE-MUTEX
> signals the blocked thread (more or less a CONDITION-NOTIFY). Two things
> you must pay attention to: SB-THREAD:GET-MUTEX needs an argument, or it
> might signal an error telling that a thread is trying to get the mutex a
> second time (of course we know that everything is OK, right?), or
> something vastly worse; and SB-THREAD:GET-MUTEX must be called before
> SB-THREAD:RELEASE-MUTEX. This is mad, of course, and I would never do
> anything like it, but maybe you can use it in some way.
> One other thing is that futex implementation of condition variables is
> broken. It will be better in a couple of weeks.
> David L. Rager wrote:
>> Greetings SBCL Folks,
>> In SBCL, is there a way to wait on a condition variable/signaling
>> mechanism without requiring a mutex? I could acquire and release a
>> thread-local mutex for each cv-wait, but I'd rather skip the locking
>> overhead if possible.
>> Thanks for your time,
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