Re: Waiting on multiple blocking events

Mike Abbott wrote:
>> Is there a way to "compose" together multiple blocking operations? 
> 
> Sounds interesting, kinda like what kqueue()/kevent() do:  one-stop
> event processing.  "Block this thread until one of this laundry list of
> disparate events fires."  Do you have a prototype implementation you'd
> like to contribute to the project, or wrappers you'd contribute to its
> "extensions" library?

I have a poor man's implementation of "cleanly interruptible points." 
This involves primitives called "hubs" (sets of threads) that threads 
may join and other threads may signal.  It's similar to a condition 
variable, but signaling results in interrupting the thread from its 
current blocking operation.

   {
     st_intr intr(hub);
     int ret = st_read_fully(...);
     if (ret == EINT) ...
     ...
   }

This turned out to be suitable enough for my purposes.  The code is all 
available in my little header of ST tools:

http://assorted.svn.sf.net/viewvc/assorted/cpp-commons/trunk/src/commons/st/st.h?revision=1077&view=markup

I thought about my more general suggestion some more.  You can implement 
any() atop ST by starting a thread for each blocking operation involved 
in the any(), wrapping them in functions that - on finishing - interrupt 
the other threads (using something similar to the above mechanism, on a 
hub created locally by the any() call), informing them that they're the 
losers (so that they may properly react/clean up), and also notifying 
the parent thread of its own success and return value.

> 
> 
> 
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-- 
Yang Zhang
http://www.mit.edu/~y_z/

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