Subj : Re: How to wait on multiple condition variables or implement a similar semantics
To   : comp.programming.threads
From : vikky@gmail.com
Date : Wed Mar 16 2005 05:41 am

Joe Seigh wrote:
> On 15 Mar 2005 18:32:02 -0800, vikky@gmail.com
<bhatnagar.vishal@gmail.com> wrote:
>
> > Hi ,
> >   I am porting an application from windows to linux. It uses
function
> > WaitForMultipleObjects() to wait on multiple events and on the
basis of
> > what event is signalled (which is specified by the functions return
> > value) it takes furthur action. The function is actually being used
> > here to wait for only two events,in mode where it returns if any of
the
> >  event is signalled. The first one being any event while the second
one
> > always being the event signalled when the application is closing.
> > I am using pthreads in linux to port the application but i got
stuck on
> > how to implement WaitForMultipleObjects() semantics. The closest
> > analogue i found to WaitForSingleObject() is using condition
variables
> > and waiting on them. But alas i can't find any function in pthread
> > library that can wait on multiple condition varibles. I want to ask
how
> > a suitable replacement for  WaitForMultipleObjects() can be made.
> >
>
> You have to use the same condition variable.
>
> For bWaitAll == true
>
> 	while (!(cond1 && cond2 && ...))
> 		pthread_cond_wait(&cvar, &mutex);
>
> >
> For bWaitAll == false
>
> 	while (!(cond1 || cond2 || ...))
> 		pthread_cond_wait(&cvar, &mutex);
>
> Use broadcast instead of signal if you have multiple waiters.
>
> There are emulations of the windows WaitForMultipleObjects out
> there, but they're pretty inefficient.  So is the windows
> implementation but that's hidden from you.
>
>
> --
> Joe Seigh

Thanks for the answer Joe but there is one problem. You suggested that
i could use multiple conditions and use their ANDing/ORing. However how
do you suggest to represent the condition pertaining to closing of the
application?

.