05-21-2011
Hi,
In my understanding for a counting semaphore (which allow an arbitrary resource count), V is = signal() and P = wait().
This User Gave Thanks to Chirel For This Post:
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
hi, is there any command where we can monitor semaphores? (1 Reply)
Discussion started by: yls177
1 Replies
2. UNIX for Dummies Questions & Answers
Hi,
I'm new to UNIX.
I need to know what's a semaphore
Do reply.
Thanks
VJ (3 Replies)
Discussion started by: vjsony
3 Replies
3. Shell Programming and Scripting
can any one tell me how to run a semaphore. i understand roughly how they work code wise, but i'm not sure how to make use of them. i have two client programs in csh that perform tasks on a server file (flat file) how the i get the semaphore to lock the file when one has accessed it and how to use... (5 Replies)
Discussion started by: FDavid
5 Replies
4. Shell Programming and Scripting
Hi,
I am looking to use a semaphore for the first time in one of my scripts. I am just wondering if there are any simple examples or tutorials around?
I am a beginner so the simpler the better :)
Thanks
-Jaken (2 Replies)
Discussion started by: Jaken
2 Replies
5. UNIX for Dummies Questions & Answers
what is semaphore? can any body explain it in a more simple way than the manual ??
replies appreciated
Regards
raguram R (7 Replies)
Discussion started by: raguramtgr
7 Replies
6. Programming
In my server code there is a thread per client...
The server call accept() and after that start the thread.
So there is a thread for client that save in RAM the client's message, that will be send to other clients.
Now in RAM I have created a shared memory in which thread read and write(save)... (2 Replies)
Discussion started by: italian_boy
2 Replies
7. Shell Programming and Scripting
Control two exclusively shared resources(semaphore). The two resources are two files. The producer will write even numbers to one file, and odd numbers to another one. The consumer respectively reads from each file until it gets 5 even numbers and 5 odd numbers.
Can any one help me with the... (0 Replies)
Discussion started by: gokult
0 Replies
8. Programming
If I create a semaphore and then I fork a number of child processes then all the child process use that same semaphore.
Since the process address spaces are different rfom each other then how all the child process are able to access the same semaphore?
I understand that semaphore/mutex is at os... (0 Replies)
Discussion started by: rupeshkp728
0 Replies
9. Solaris
Can anyone tell me abt the Semaphore concept and what is semaphore???
is semaphore id is associated in terms as in resources like semaphore id 1 indicates cpu share unit is given and semaphore id 2 will indicate abt the memore or semaphore id 3 will tell us the i/o components (1 Reply)
Discussion started by: aarjun07
1 Replies
10. UNIX for Beginners Questions & Answers
I was asked to add this piece of code to a c program which I will execute through the shell:
for(long i = 0; i < NITER; i++)
{ sem_wait( &sema);
count++;
sem_post( &sema); }
I didn't get it, which is the critical section ? if it's "count++" how would a thread wake up in order to enter it... (1 Reply)
Discussion started by: uniran
1 Replies
LEARN ABOUT DEBIAN
coro::semaphoreset
SemaphoreSet(3pm) User Contributed Perl Documentation SemaphoreSet(3pm)
NAME
Coro::SemaphoreSet - efficient set of counting semaphores
SYNOPSIS
use Coro;
$sig = new Coro::SemaphoreSet [initial value];
$sig->down ("semaphoreid"); # wait for signal
# ... some other "thread"
$sig->up ("semaphoreid");
DESCRIPTION
This module implements sets of counting semaphores (see Coro::Semaphore). It is nothing more than a hash with normal semaphores as members,
but is more efficiently managed.
This is useful if you want to allow parallel tasks to run in parallel but not on the same problem. Just use a SemaphoreSet and lock on the
problem identifier.
You don't have to load "Coro::SemaphoreSet" manually, it will be loaded automatically when you "use Coro" and call the "new" constructor.
new [inital count]
Creates a new semaphore set with the given initial lock count for each individual semaphore. See Coro::Semaphore.
$semset->down ($id)
Decrement the counter, therefore "locking" the named semaphore. This method waits until the semaphore is available if the counter is
zero.
$semset->up ($id)
Unlock the semaphore again. If the semaphore reaches the default count for this set and has no waiters, the space allocated for it will
be freed.
$semset->try ($id)
Try to "down" the semaphore. Returns true when this was possible, otherwise return false and leave the semaphore unchanged.
$semset->count ($id)
Return the current semaphore count for the specified semaphore.
$semset->waiters ($id)
Returns the number (in scalar context) or list (in list context) of waiters waiting on the specified semaphore.
$semset->wait ($id)
Same as Coro::Semaphore::wait on the specified semaphore.
$guard = $semset->guard ($id)
This method calls "down" and then creates a guard object. When the guard object is destroyed it automatically calls "up".
$semaphore = $semset->sem ($id)
This SemaphoreSet version is based on Coro::Semaphore's. This function creates (if necessary) the underlying Coro::Semaphore object and
returns it. You may legally call any Coro::Semaphore method on it, but note that calling "$semset->up" can invalidate the returned
semaphore.
AUTHOR
Marc Lehmann <schmorp@schmorp.de>
http://home.schmorp.de/
perl v5.14.2 2012-04-13 SemaphoreSet(3pm)