From: Aaron Bannert <aaron@apache.org>
Date: Sun, 28 Apr 2002 22:25:16 +0000 (+0000)
Subject: Some threadpool fixes:
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f00ec6fdf1ec1ab40dc75b17cab0640290527220;p=apache

Some threadpool fixes:

- We don't need the listener_blocked flag, just check if the element
  we're adding makes the stack non-empty.
- When we are terminated, return APR_EOF; catch this event in the
  worker thread and the listener thread.
- When shutting down, always signal a potential listener thread.
- Wait to signal the listener thread until after we add the worker
  element to the stack.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94841 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/server/mpm/experimental/threadpool/threadpool.c b/server/mpm/experimental/threadpool/threadpool.c
index a1c122af99..33f4a17ad4 100644
--- a/server/mpm/experimental/threadpool/threadpool.c
+++ b/server/mpm/experimental/threadpool/threadpool.c
@@ -269,7 +269,6 @@ typedef struct {
 typedef struct {
     apr_thread_mutex_t *mutex;
     apr_thread_cond_t *cond;
-    int listener_blocked;
     worker_wakeup_info **stack;
     apr_size_t nelts;
     apr_size_t nalloc;
@@ -288,7 +287,6 @@ static worker_stack* worker_stack_create(apr_pool_t *pool, apr_size_t max)
     if ((rv = apr_thread_cond_create(&stack->cond, pool)) != APR_SUCCESS) {
         return NULL;
     }
-    stack->listener_blocked = 0;
     stack->nelts = 0;
     stack->nalloc = max;
     stack->stack =
@@ -307,27 +305,32 @@ static apr_status_t worker_stack_wait(worker_stack *stack,
         return rv;
     }
     if (stack->terminated) {
-        wakeup->csd = NULL;
         if ((rv = apr_thread_mutex_unlock(stack->mutex)) != APR_SUCCESS) {
             return rv;
         }
-        return APR_EINTR;
+        return APR_EOF;
     }
     if (stack->nelts == stack->nalloc) {
-        (void)apr_thread_mutex_unlock(stack->mutex);
-        return APR_ENOSPC;
-    }
-    if (stack->listener_blocked) {
-        stack->listener_blocked = 0;
-        if ((rv = apr_thread_cond_signal(stack->cond)) !=
-            APR_SUCCESS) {
+        if ((rv = apr_thread_mutex_unlock(stack->mutex)) != APR_SUCCESS) {
             return rv;
         }
+        return APR_ENOSPC;
+    }
+    stack->stack[stack->nelts] = wakeup;
+    /* Signal a blocking listener thread only if we just made the
+     * stack non-empty. */
+    if (stack->nelts++ == 0) {
+        (void)apr_thread_cond_signal(stack->cond);
     }
-    stack->stack[stack->nelts++] = wakeup;
     if ((rv = apr_thread_mutex_unlock(stack->mutex)) != APR_SUCCESS) {
         return rv;
     }
+
+    /* At this point we've already added this worker to the stack, now
+     * we just wait until the listener has accept()ed a connection
+     * for us. */
+    /* FIXME: We must own the wakeup->mutex before calling cond_wait(),
+     * and then keep calling cond_wait() until some signal is met. */
     if ((rv = apr_thread_cond_wait(wakeup->cond, wakeup->mutex)) !=
         APR_SUCCESS) {
         return rv;
@@ -342,15 +345,22 @@ static apr_status_t worker_stack_pop(worker_stack *stack,
     if ((rv = apr_thread_mutex_lock(stack->mutex)) != APR_SUCCESS) {
         return rv;
     }
-    if (stack->nelts == 0) {
-        stack->listener_blocked = 1;
-        if ((rv = apr_thread_cond_wait(stack->cond, stack->mutex)) !=
-            APR_SUCCESS) {
+    while ((stack->nelts == 0) && (!stack->terminated)) {
+        rv = apr_thread_cond_wait(stack->cond, stack->mutex);
+        if (rv != APR_SUCCESS) {
+            apr_status_t rv2;
+            rv2 = apr_thread_mutex_unlock(stack->mutex);
+            if (rv2 != APR_SUCCESS) {
+                return rv2;
+            }
             return rv;
         }
+    }
+    if (stack->terminated) {
         if ((rv = apr_thread_mutex_unlock(stack->mutex)) != APR_SUCCESS) {
             return rv;
         }
+        return APR_EOF;
     }
     *worker = stack->stack[--stack->nelts];
     if ((rv = apr_thread_mutex_unlock(stack->mutex)) != APR_SUCCESS) {
@@ -394,12 +404,9 @@ static void wakeup_listener(void)
     if ((rv = apr_thread_mutex_lock(idle_worker_stack->mutex)) != APR_SUCCESS) {
         return;
     }
-    if (idle_worker_stack->listener_blocked) {
-        idle_worker_stack->listener_blocked = 0;
-        if ((rv = apr_thread_cond_signal(idle_worker_stack->cond)) !=
-            APR_SUCCESS) {
-            return;
-        }
+    if ((rv = apr_thread_cond_signal(idle_worker_stack->cond)) !=
+        APR_SUCCESS) {
+        return;
     }
     if ((rv = apr_thread_mutex_unlock(idle_worker_stack->mutex)) != APR_SUCCESS) {
         return;
@@ -844,8 +851,11 @@ static void *listener_thread(apr_thread_t *thd, void * dummy)
         if (listener_may_exit) break;
 
         if (worker == NULL) {
-            if ((rv = worker_stack_pop(idle_worker_stack, &worker)) !=
-                APR_SUCCESS) {
+            rv = worker_stack_pop(idle_worker_stack, &worker);
+            if (APR_STATUS_IS_EOF(rv)) {
+                break;
+            }
+            else if (rv != APR_SUCCESS) {
                 ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf,
                              "worker_stack_pop failed");
                 break;
@@ -1034,9 +1044,13 @@ static void * APR_THREAD_FUNC worker_thread(apr_thread_t *thd, void * dummy)
     while (!workers_may_exit) {
         ap_update_child_status_from_indexes(process_slot, thread_slot, SERVER_READY, NULL);
         rv = worker_stack_wait(idle_worker_stack, wakeup);
-        if ((rv != APR_SUCCESS) || workers_may_exit ||
-            (wakeup->csd == NULL)) {
-            break;
+        if (APR_STATUS_IS_EOF(rv)) {
+            break; /* The queue has been terminated. */
+        }
+        else if (rv != APR_SUCCESS) {
+            ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf,
+                         "worker_stack_wait failed");
+            break; /* Treat all other errors as fatal. */
         }
         process_socket(ptrans, wakeup->csd,
                        process_slot, thread_slot, bucket_alloc);