Fixed timer and event race condition.

When idle timeout occurs at the same time as a request comes in,
the timer handler closes connection while the read event triggers
request processing, and this eventually leads to segmentation fault.

src/nxt_conn.h

@@ -157,7 +157,8 @@ struct nxt_conn_s {
     nxt_sockaddr_t                *local;
     const char                    *action;
 
-    uint8_t                       blocked;      /* 1 bit */
+    uint8_t                       block_read;   /* 1 bit */
+    uint8_t                       block_write;  /* 1 bit */
     uint8_t                       delayed;      /* 1 bit */
 
 #define NXT_CONN_SENDFILE_OFF     0

src/nxt_conn_read.c

@@ -45,10 +45,11 @@ nxt_conn_io_read(nxt_task_t *task, void *obj, void *data)
 
     c = obj;
 
-    nxt_debug(task, "conn read fd:%d rdy:%d cl:%d",
+    nxt_debug(task, "conn read fd:%d rdy:%d cl:%d er:%d bl:%d",
-              c->socket.fd, c->socket.read_ready, c->socket.closed);
+              c->socket.fd, c->socket.read_ready, c->socket.closed,
+              c->socket.error, c->block_read);
 
-    if (c->socket.error != 0) {
+    if (c->socket.error != 0 || c->block_read) {
         return;
     }
 

src/nxt_conn_write.c

@@ -22,9 +22,10 @@ nxt_conn_io_write(nxt_task_t *task, void *obj, void *data)
 
     c = obj;
 
-    nxt_debug(task, "conn write fd:%d", c->socket.fd);
+    nxt_debug(task, "conn write fd:%d er:%d bl:%d",
+              c->socket.fd, c->socket.error, c->block_write);
 
-    if (c->socket.error != 0) {
+    if (c->socket.error != 0 || c->block_write) {
         goto error;
     }
 

src/nxt_event_conn_job_sendfile.c

@@ -80,7 +80,8 @@ nxt_event_conn_job_sendfile_start(nxt_task_t *task, void *obj, void *data)
             c->write = NULL;
             jbs->ready_handler = nxt_event_conn_job_sendfile_return;
 
-            c->blocked = 1;
+            c->block_read = 1;
+            c->block_write = 1;
 
             nxt_job_start(task, &jbs->job, nxt_event_conn_job_sendfile_handler);
             return;
@@ -170,7 +171,8 @@ nxt_event_conn_job_sendfile_return(nxt_task_t *task, void *obj, void *data)
     jbs = obj;
     c = data;
 
-    c->blocked = 0;
+    c->block_read = 0;
+    c->block_write = 0;
 
     sent = jbs->sent;
     c->sent += sent;

src/nxt_h1proto.c

@@ -1220,6 +1220,7 @@ nxt_h1p_conn_request_timeout(nxt_task_t *task, void *obj, void *data)
     nxt_debug(task, "h1p conn request timeout");
 
     c = nxt_read_timer_conn(timer);
+    c->block_read = 1;
     /*
      * Disable SO_LINGER off during socket closing
      * to send "408 Request Timeout" error response.
@@ -1250,6 +1251,7 @@ nxt_h1p_conn_request_send_timeout(nxt_task_t *task, void *obj, void *data)
     nxt_debug(task, "h1p conn request send timeout");
 
     c = nxt_write_timer_conn(timer);
+    c->block_write = 1;
     h1p = c->socket.data;
 
     nxt_h1p_request_error(task, h1p, h1p->request);
@@ -1464,6 +1466,7 @@ nxt_h1p_idle_timeout(nxt_task_t *task, void *obj, void *data)
     nxt_debug(task, "h1p idle timeout");
 
     c = nxt_read_timer_conn(timer);
+    c->block_read = 1;
 
     nxt_h1p_idle_response(task, c);
 }
@@ -1559,6 +1562,7 @@ nxt_h1p_idle_response_timeout(nxt_task_t *task, void *obj, void *data)
     nxt_debug(task, "h1p idle timeout response timeout");
 
     c = nxt_read_timer_conn(timer);
+    c->block_write = 1;
 
     nxt_h1p_shutdown(task, c);
 }