Re: [Discuss-gnuradio] Linux Semaphores

[Eric Blossom]

On Thu, Oct 26, 2006 at 10:43:08AM +0800, Jeremy Chew wrote:
> I'm working on developing  TDMA on GR using RedHat Enterprise Linux WS 2.6. 
> I intend to use semaphores or mutex for controlling access to shared memory 
> when events like packet arrivals and timeouts occur.

OK

> However, I understand based on the man pages that a number of the calls for 
> semaphores and mutex may cause a deadlock when the calling thread happens 
> to be handling an asynchronous signal.

OK

> First of all, what are asynchronous signals in this context?

They mean "signals" as defined by the kernel system calls
signal(2), kill(2), sigaction(2), etc.  Try "man sigaction"

> If they refer to events whose time occurance is unpredictable,
> wouldn't such signals apply to a really large number of cases,
> including packet arrivals?

No.

> The man pages say that sem_post is the only POSIX call that handles 
> asynchronous signals fine. What use is this if I can't use sem_wait with 
> asynchronous signals?
> 
> What is your experience with semaphores and mutex?

More years than I like to think about ;)

You may want to spend some time with a good book on Unix or Linux
programming.  Sorry, I don't have a specific recommendation.

Eric