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Fix for thread/fork problem. Don't start a worker thread until one is

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needed.
This commit is contained in:
Mark Valence 2000-06-21 06:09:45 +00:00
parent b065b258f4
commit 719b945c78
1 changed files with 37 additions and 11 deletions
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48
libraries/libldap_r/tpool.c
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@ -44,6 +44,7 @@ struct ldap_int_thread_pool_s {
long ltp_pending_count;
long ltp_active_count;
long ltp_open_count;
long ltp_starting;
};
typedef struct ldap_int_thread_ctx_s {
@ -87,9 +88,8 @@ ldap_pvt_thread_pool_init (
int max_concurrency,
int max_pending )
{
int rc;
ldap_pvt_thread_pool_t pool;
ldap_pvt_thread_t thr;
int rc;
*tpool = NULL;
pool = (ldap_pvt_thread_pool_t) LDAP_CALLOC(1,
@ -97,8 +97,12 @@ ldap_pvt_thread_pool_init (
if (pool == NULL) return(-1);
ldap_pvt_thread_mutex_init(&pool->ltp_mutex);
ldap_pvt_thread_cond_init(&pool->ltp_cond);
rc = ldap_pvt_thread_mutex_init(&pool->ltp_mutex);
if (rc != 0)
return(rc);
rc = ldap_pvt_thread_cond_init(&pool->ltp_cond);
if (rc != 0)
return(rc);
pool->ltp_state = LDAP_INT_THREAD_POOL_RUNNING;
pool->ltp_max_count = max_concurrency;
pool->ltp_max_pending = max_pending;
@ -106,9 +110,24 @@ ldap_pvt_thread_pool_init (
ldap_int_thread_enlist(&ldap_int_thread_pool_list, pool);
ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
/* start up one thread, just so there is one */
#if 0
/* THIS WILL NOT WORK on some systems. If the process
* forks after starting a thread, there is no guarantee
* that the thread will survive the fork. For example,
* slapd forks in order to daemonize, and does so after
* calling ldap_pvt_thread_pool_init. On some systems,
* this initial thread does not run in the child process,
* but ltp_open_count == 1, so two things happen:
* 1) the first client connection fails, and 2) when
* slapd is kill'ed, it never terminates since it waits
* for all worker threads to exit.
/* start up one thread, just so there is one. no need to
* lock the mutex right now, since no threads are running.
*/
pool->ltp_open_count++;
ldap_pvt_thread_t thr;
rc = ldap_pvt_thread_create( &thr, 1,
(void *) ldap_int_thread_pool_wrapper, pool );
@ -122,6 +141,7 @@ ldap_pvt_thread_pool_init (
free(pool);
return(-1);
}
#endif
*tpool = pool;
return(0);
@ -172,6 +192,7 @@ ldap_pvt_thread_pool_submit (
|| pool->ltp_open_count < pool->ltp_max_count))
{
pool->ltp_open_count++;
pool->ltp_starting++;
need_thread = 1;
}
ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
@ -179,15 +200,17 @@ ldap_pvt_thread_pool_submit (
if (need_thread) {
int rc = ldap_pvt_thread_create( &thr, 1,
(void *)ldap_int_thread_pool_wrapper, pool );
if (rc != 0) {
ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
if (rc == 0) {
pool->ltp_starting--;
} else {
/* couldn't create thread. back out of
* ltp_open_count and check for even worse things.
*/
ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
pool->ltp_open_count--;
pool->ltp_starting--;
if (pool->ltp_open_count == 0) {
/* no open threads at all?!? this will never happen
* because we always leave at least one thread open.
/* no open threads at all?!?
*/
if (ldap_int_thread_delist(&pool->ltp_pending_list, ctx)) {
/* no open threads, context not handled, so
@ -200,13 +223,13 @@ ldap_pvt_thread_pool_submit (
return(-1);
}
}
ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
/* there is another open thread, so this
* context will be handled eventually.
* continue on and signal that the context
* is waiting.
*/
}
ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
}
return(0);
@ -305,7 +328,10 @@ ldap_int_thread_pool_wrapper (
/* we could check an idle timer here, and let the
* thread die if it has been inactive for a while.
* only die if there are other open threads (i.e.,
* always have at least one thread open).
* always have at least one thread open). the check
* should be like this:
* if (pool->ltp_open_count > 1 && pool->ltp_starting == 0)
* check timer, leave thread (break;)
*/
if (pool->ltp_state == LDAP_INT_THREAD_POOL_RUNNING)