Programming

I have a problem with a C multi-threaded program I am writing. I cannot figure out how to keep the unique key value at the thread level. I wrote a program in C that forked a bunch of processes and then decided to convert it to threads and I can't keep the key unique to each thread. In a nutshell it reads a file with a valid pathname on every line (approx 200) and starts a thread to watch over a unique directory (simple polling program). Error is when I create a new thread, then every pre-exisiting thread is looking at the last pathname read in. So I end up with 200+ threads watching the same directory.

Following is what I think is a big enough snippet from main and the pthread_create sub to give something for someone to point out what I am doing wrong. Thanks in advance, Jennifer


> MAIN
> --------
> pthread_t main_thr;
> pthread_t thr;
> pthread_attr_t attr;
>
> main_thr = pthread_self();
> p=malloc(2);
> p = buffer;void *watch_dir(void *arg)
>
> pthread_key_t key;
>
> pthread_key_create(&key, NULL);
> thread_setspecific(key, arg);
> arg=pthread_getspecific(key);
> pthread_attr_init(&attr);
> pthread_attr_setdetachstate(&attr, 1);
>
> if (pthread_create(&thr, &attr, watch_dir, p))
> {
> fprintf(fplog, "Can't create thr\n"), exit(1);
> }
>
> WATCH_DIR
> ------------------
> void *watch_dir(void *arg)
> {
>
> FILE *fplog;
> time_t curtime;
> struct tm *loctime;
> DIR *dir_p;
> struct dirent *dir_entry_p;
> pthread_key_t key;
> pthread_key_create(&key, NULL);
> pthread_setspecific(key, arg);
> arg=pthread_getspecific(key);
>
> for (;
> {
> fplog=fopen(FTP_LOG, "a");
>
> curtime = time (NULL); /* get current time */
> loctime = localtime (&curtime);
> fputs (asctime (loctime), fplog);
> sleep(3);
>
>
> dir_p = opendir(arg);
> while( NULL != (dir_entry_p = readdir(dir_p)))
> {
> if (!((strcmp(dir_entry_p->d_name, ".") == 0) ||
> (strcmp(dir_entry_p->d_name, "..") == 0)))
> {
> fprintf(fplog," %s \n", dir_entry_p->d_name);
> /*
> holder for FTP Control PERL script
> send: arg & dir_entry_p->d_name
> directory & filename
> */
> }
> /*
> printf("p is %s\n",p);
>

my eyes, they burn. code tags please. Like {code} int main(); {/code} except with [ ]. This will use a monospace font, preserve indenting, and prevent syntax being converted to smilies.

What is buffer? What is the malloc(2) for, especially since the allocated memory immediately gets lost when you point it to buffer instead? I suspect you're using pointers to a common buffer, which gets overwritten every time a new string is read.

Got it fixed. It was more related to converting from Solarix to AIX than anything else. Not sure what is meant by putting in tags so the smiles don't creep in though ..... --Jennifer

Without tags:

> for (;
> {
> something;
> }

With tags:

Code:

for(;;)
{
  something;
}

[ code ] for(; { ... } [ / code ]

Remove the spaces between the [ ] 's to make the tags work like the code block above it.