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Full Discussion: Semaphore
Top Forums Programming Semaphore Post 302407340 by italian_boy on Thursday 25th of March 2010 06:52:12 AM
Old 03-25-2010
Semaphore
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) client's message :

server.c

Code:
Code:
socket()
bind()
..
...
...int shmid;
    key_t key;
    char *shm, *s;

    key = 5678;

    if ((shmid = shmget(key, 10000, IPC_CREAT | 0666)) < 0) {
        perror("shmget");
        exit(1);
    }

    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
        perror("shmat");
        exit(1);
    }
   int *mem=mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, shmid, 0);
     ftruncate(shmid, 4096); 

while(1){
...
...
...
}

Now I must synchronized the threads by semaphore to read and write into shared memory.Like this : all thread can read, but when a thread write other thread can't do anything , only WAIT that the writing thread signals it has finished. I don't know how can I do... Can someone help me with some example? how can I manage a semaphore??
Thank you very much!
Last edited by pludi; 03-25-2010 at 07:57 AM.. Reason: code tags, please...
 

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LEARN ABOUT DEBIAN

bup-server

bup-server(1)						      General Commands Manual						     bup-server(1)

NAME

       bup-server - the server side of the bup client-server relationship

SYNOPSIS

       bup server

DESCRIPTION

       bup server  is  the  server  side of a remote bup session.  If you use bup-split(1) or bup-save(1) with the -r option, they will ssh to the
       remote server and run bup server to receive the transmitted objects.

       There is normally no reason to run bup server yourself.

MODES

       smart  In this mode, the server checks each incoming object against the idx files in its repository.  If  any  object  already  exists,	it
	      tells  the  client  about  the  idx file it was found in, allowing the client to download that idx and avoid sending duplicate data.
	      This is bup-server's default mode.

       dumb   In this mode, the server will not check its local index before writing an object.  To avoid writing duplicate  objects,  the  server
	      will tell the client to download all of its .idx files at the start of the session.  This mode is useful on low powered server hard-
	      ware (ie router/slow NAS).

FILES

       $BUP_DIR/bup-dumb-server
	      Activate dumb server mode, as discussed above.  This file is not created by default in new repositories.

SEE ALSO

       bup-save(1), bup-split(1)

BUP

       Part of the bup(1) suite.

AUTHORS

       Avery Pennarun <apenwarr@gmail.com>.

Bup unknown-															     bup-server(1)
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