9 More Discussions You Might Find Interesting
1. Solaris
Hi,
Can somebody please explain me what semaphores are? there purpose? and there effects?
Thanks in advance:) (0 Replies)
Discussion started by: Laxxi
0 Replies
2. Solaris
Hi, I've used the following way to set ssh public key authentication and it is working fine on Solaris 10, RedHat Linux and SuSE Linux servers without any problem. But I got error 'Server refused our key' on Solaris 8 system. Solaris 8 uses SSH2 too. Why? Please help. Thanks.
... (1 Reply)
Discussion started by: aixlover
1 Replies
3. UNIX for Dummies Questions & Answers
I am having problem with semaphores. I am trying to protect line where process prints so that every process with print in proper order.This is the code..
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/types.h>
union... (3 Replies)
Discussion started by: joker40
3 Replies
4. UNIX for Advanced & Expert Users
Hello, first of all I apologize if this thread is not in the correct section of this forum, but this one just seemed the most appropriate.
The question I have does not concern Unix specifically, it applies to virtually any OS, however it is in Unix where I learned about this problem.
So, the... (8 Replies)
Discussion started by: Watto86
8 Replies
5. Programming
been searching around on how to use an up and down function with semaphores but i can't find an example. i looked into using: "semop" but i have no idea how to use it. I have been able to declared the semaphores using semget and initializing them using semctl. (7 Replies)
Discussion started by: ddx08
7 Replies
6. Shell Programming and Scripting
Hi Friends,
If i execute this command it comes back with 300 lines:
ipcs|grep cerebrus >>> i would like to clear the semaphores but ipcrm can remove one id at a time. is there a quicker way of removing semaphores maybe using awk?
Regards, (1 Reply)
Discussion started by: kekanap
1 Replies
7. Programming
Hi there,
Could someone please confirm which POSIX semaphore routines should be used for a multiprocess (and not multithreaded) environment?
sys/sem.h definitely works. but the routines, semget, semctl, semop are pretty unwieldy. So, I am looking for an easier way out.
From the man pages... (2 Replies)
Discussion started by: qntmteleporter
2 Replies
8. UNIX for Dummies Questions & Answers
Hi all,
I am using HP 10.20 on A 9000/785. My question is:
If I am the only person logged in as root at the moment, how many "semaphore proccesses" should I have?? Is it only one, or it is relevant to other system proccesses?
Here is what I get listing the current semaphores
# ipcs -sp... (1 Reply)
Discussion started by: guest100
1 Replies
9. Programming
Dear Reader,
I'm in a multiprocess environment working with shared mem and semaphores as mutex.. The problem is -- If one of the process hooked up with the semaphore and accessing the shared mem, terminates abruptly ( or got killed ), other process which are in want of the semaphore are... (1 Reply)
Discussion started by: joseph_shibu
1 Replies
Thread::Semaphore(3pm) Perl Programmers Reference Guide Thread::Semaphore(3pm)
NAME
Thread::Semaphore - thread-safe semaphores
SYNOPSIS
use Thread::Semaphore;
my $s = new Thread::Semaphore;
$s->up; # Also known as the semaphore V -operation.
# The guarded section is here
$s->down; # Also known as the semaphore P -operation.
# The default semaphore value is 1.
my $s = new Thread::Semaphore($initial_value);
$s->up($up_value);
$s->down($up_value);
DESCRIPTION
Semaphores provide a mechanism to regulate access to resources. Semaphores, unlike locks, aren't tied to particular scalars, and so may be
used to control access to anything you care to use them for.
Semaphores don't limit their values to zero or one, so they can be used to control access to some resource that there may be more than one
of. (For example, filehandles). Increment and decrement amounts aren't fixed at one either, so threads can reserve or return multiple
resources at once.
FUNCTIONS AND METHODS
new
new NUMBER
"new" creates a new semaphore, and initializes its count to the passed number. If no number is passed, the semaphore's count is set
to one.
down
down NUMBER
The "down" method decreases the semaphore's count by the specified number, or by one if no number has been specified. If the sema-
phore's count would drop below zero, this method will block until such time that the semaphore's count is equal to or larger than
the amount you're "down"ing the semaphore's count by.
up
up NUMBER
The "up" method increases the semaphore's count by the number specified, or by one if no number has been specified. This will
unblock any thread blocked trying to "down" the semaphore if the "up" raises the semaphore count above the amount that the "down"s
are trying to decrement it by.
perl v5.8.0 2002-06-01 Thread::Semaphore(3pm)