Fixed handling of already closed connections.

In limit_req, auth_delay, and upstream code to check for broken
connections, tests for possible connection close by the client
did not work if the connection was already closed when relevant
event handler was set.  This happened because there were no additional
events in case of edge-triggered event methods, and read events
were disabled in case of level-triggered ones.

Fix is to explicitly post a read event if the c->read->ready flag
is set.

src/http/modules/ngx_http_limit_req_module.c

diff --git a/src/http/modules/ngx_http_limit_req_module.c b/src/http/modules/ngx_http_limit_req_module.c
index dad5edb..2b062a3 100644
--- a/src/http/modules/ngx_http_limit_req_module.c
+++ b/src/http/modules/ngx_http_limit_req_module.c
@@ -310,8 +310,13 @@
 
     r->main->limit_req_status = NGX_HTTP_LIMIT_REQ_DELAYED;
 
-    if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
-        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    if (r->connection->read->ready) {
+        ngx_post_event(r->connection->read, &ngx_posted_events);
+
+    } else {
+        if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
+            return NGX_HTTP_INTERNAL_SERVER_ERROR;
+        }
     }
 
     r->read_event_handler = ngx_http_test_reading;

src/http/ngx_http_core_module.c

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 67476e7..9b94b32 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -1190,8 +1190,13 @@
     ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
                   "delaying unauthorized request");
 
-    if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
-        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    if (r->connection->read->ready) {
+        ngx_post_event(r->connection->read, &ngx_posted_events);
+
+    } else {
+        if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
+            return NGX_HTTP_INTERNAL_SERVER_ERROR;
+        }
     }
 
     r->read_event_handler = ngx_http_test_reading;

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index bd1627c..1016afa 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -608,9 +608,14 @@
 
     if (!u->store && !r->post_action && !u->conf->ignore_client_abort) {
 
-        if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
-            ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
-            return;
+        if (r->connection->read->ready) {
+            ngx_post_event(r->connection->read, &ngx_posted_events);
+
+        } else {
+            if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
+                ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
+                return;
+            }
         }
 
         r->read_event_handler = ngx_http_upstream_rd_check_broken_connection;