Is There Something like a Semaphore with Specifiable Timeout

clusardi2k@aol.com · *nix forums beginner Joined: 19 Jul 2005 Posts: 40

Hello,

I am looking for instructions that do what a mutual exclusive
semaphore does but with some specifiable timeout for SGI and Red
Hat Linux. (I.E.: A Semaphore with a count of 1 but with a timeout)

In other words, I want to know how to guard a critical piece of
code, but I don't want to be forced to wait a long time in a
queue. In other words, I have processes that could go on living
without entering the critical section of code.

Thank you,
Christopher Lusardi

Tony 'Nicoya' Mantler · *nix forums Guru Wannabe Joined: 02 Jul 2005 Posts: 139

In article <1121774738.656254.234040@g49g2000cwa.googlegroups.com>,
clusardi2k@aol.com wrote:

: Hello,
:
: I am looking for instructions that do what a mutual exclusive
: semaphore does but with some specifiable timeout for SGI and Red
: Hat Linux. (I.E.: A Semaphore with a count of 1 but with a timeout)
:
:
: In other words, I want to know how to guard a critical piece of
: code, but I don't want to be forced to wait a long time in a
: queue. In other words, I have processes that could go on living
: without entering the critical section of code.

The pthread condvar functions support a timeout while waiting (through
pthread_cond_timedwait()), but it would probably be a bit silly to use a condvar
as a mutex, depending on your application.

If your application would perform adequately with no waiting at all, you can use
trylock variants of your usual locking calls (like pthread_mutex_trylock()).

I would suggest against using alarm() to time out locking calls. Going down that
route will make a *really* big mess of things.

It's hard to say what the right solution for you is without knowing more about
the nature of your code.

Cheers - Tony 'Nicoya' Mantler :)

--
Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca
-- http://nicoya.feline.pp.se/ -- http://www.ubb.ca/ --

Brent Casavant · *nix forums beginner Joined: 28 Jul 2005 Posts: 2

On Tue, 19 Jul 2005 clusardi2k@aol.com wrote:

Tony 'Nicoya' Mantler · *nix forums Guru Wannabe Joined: 02 Jul 2005 Posts: 139

In article <20050728144632.W5118@chenjesu.americas.sgi.com>,
Brent Casavant <bcasavan@angeltread.org> wrote:

: On Tue, 19 Jul 2005 clusardi2k@aol.com wrote:
:
: > I am looking for instructions that do what a mutual exclusive
: > semaphore does but with some specifiable timeout for SGI and Red
: > Hat Linux. (I.E.: A Semaphore with a count of 1 but with a timeout)
: >
: >
: > In other words, I want to know how to guard a critical piece of
: > code, but I don't want to be forced to wait a long time in a
: > queue. In other words, I have processes that could go on living
: > without entering the critical section of code.
:
: Assuming you're using IRIX, usopenpollsema(3P) should steer you
: in the right direction.

Linux has semtimedop(), which I don't think is available in IRIX. I neglected to
mention it in my previous post.

There doesn't seem to be much love for cross-platform compatibility in this area.

Cheers - Tony 'Nicoya' Mantler :)

--
Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca
-- http://nicoya.feline.pp.se/ -- http://www.ubb.ca/ --

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