[nginx] Thread pools: fixed the waiting tasks accounting.

[Ruslan Ermilov]

details:   http://hg.nginx.org/nginx/rev/25fda43e3bcb
branches:  
changeset: 6026:25fda43e3bcb
user:      Ruslan Ermilov <ru at nginx.com>
date:      Thu Mar 19 13:00:48 2015 +0300
description:
Thread pools: fixed the waiting tasks accounting.

Behave like POSIX semaphores.  If N worker threads are waiting for tasks,
at least that number of tasks should be allowed to be put into the queue.

diffstat:

 src/core/ngx_thread_pool.c |  15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diffs (60 lines):

diff -r 32099b107191 -r 25fda43e3bcb src/core/ngx_thread_pool.c
--- a/src/core/ngx_thread_pool.c	Thu Mar 19 23:19:35 2015 +0300
+++ b/src/core/ngx_thread_pool.c	Thu Mar 19 13:00:48 2015 +0300
@@ -25,7 +25,7 @@ typedef struct {
 
 struct ngx_thread_pool_s {
     ngx_thread_pool_queue_t   queue;
-    ngx_uint_t                waiting;
+    ngx_int_t                 waiting;
     ngx_thread_cond_t         cond;
 
     ngx_log_t                *log;
@@ -33,7 +33,7 @@ struct ngx_thread_pool_s {
 
     ngx_str_t                 name;
     ngx_uint_t                threads;
-    ngx_uint_t                max_queue;
+    ngx_int_t                 max_queue;
 
     u_char                   *file;
     ngx_uint_t                line;
@@ -219,7 +219,7 @@ ngx_thread_task_post(ngx_thread_pool_t *
         (void) ngx_thread_mutex_unlock(&tp->queue.mtx, tp->log);
 
         ngx_log_error(NGX_LOG_ERR, tp->log, 0,
-                      "thread pool \"%V\" queue overflow: %ui tasks waiting",
+                      "thread pool \"%V\" queue overflow: %i tasks waiting",
                       &tp->name, tp->waiting);
         return NGX_ERROR;
     }
@@ -283,7 +283,10 @@ ngx_thread_pool_cycle(void *data)
             return NULL;
         }
 
-        while (tp->waiting == 0) {
+        /* the number may become negative */
+        tp->waiting--;
+
+        while (tp->queue.first == NULL) {
             if (ngx_thread_cond_wait(&tp->cond, &tp->queue.mtx, tp->log)
                 != NGX_OK)
             {
@@ -292,8 +295,6 @@ ngx_thread_pool_cycle(void *data)
             }
         }
 
-        tp->waiting--;
-
         task = tp->queue.first;
         tp->queue.first = task->next;
 
@@ -476,7 +477,7 @@ ngx_thread_pool(ngx_conf_t *cf, ngx_comm
 
             tp->max_queue = ngx_atoi(value[i].data + 10, value[i].len - 10);
 
-            if (tp->max_queue == (ngx_uint_t) NGX_ERROR) {
+            if (tp->max_queue == NGX_ERROR) {
                 ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                    "invalid max_queue value \"%V\"", &value[i]);
                 return NGX_CONF_ERROR;