Subj : Re: signaling threads from a forked child?
To   : comp.programming.threads
From : Joe Seigh
Date : Fri Aug 05 2005 07:52 am

markh@compro.net wrote:
> I'm attempting to use pthread_cond_signal in the child directed to  a
> particular thread using the parents Mutex and cond variable. I've used
> the pthread_atfork call to insure the child has initialized it's copy
> of the Mutex and cond variable. I gues thats the real issue here. The
> childs copy of the Mutex and cond variable are not the same physical
> memory as the parents and parents thread.
> 
>  It appears to me that the only real reason that this doesn't  work
> might be because the the childs copy of the Mutex and cond variable are
> not the same as the parents and parents thread. The thread is in a
> pthread_cond_wait.
> 
> Does the thread even know or care where or by whom the the cond
> variable is satisfied. When the cond  gets satisfied the thread should
> wake up.  How do I satisfy the cond  from a child? 
> 
You have to set the mutex and condvar in a shared memory segment and
use the process shared attribute assuming it's supported.  Or use
IPC semaphores or select() w/ a pipe fd or unix signals as mentioned
before.

There's a **REASON** you think you need to wait.  There may be a real
simple solution based on the mechanism associated with that reason.


-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

.