use non-blocking open() not to hang on FIFO files, etc.

src/core/ngx_open_file_cache.c

diff --git a/src/core/ngx_open_file_cache.c b/src/core/ngx_open_file_cache.c
index 6aa66fd..a9c4532 100644
--- a/src/core/ngx_open_file_cache.c
+++ b/src/core/ngx_open_file_cache.c
@@ -490,7 +490,14 @@
     }
 
     if (!of->log) {
-        fd = ngx_open_file(name, NGX_FILE_RDONLY, NGX_FILE_OPEN, 0);
+
+        /*
+         * Use non-blocking open() not to hang on FIFO files, etc.
+         * This flag has no effect on a regular files.
+         */
+
+        fd = ngx_open_file(name, NGX_FILE_RDONLY|NGX_FILE_NONBLOCK,
+                           NGX_FILE_OPEN, 0);
 
     } else {
         fd = ngx_open_file(name, NGX_FILE_APPEND, NGX_FILE_CREATE_OR_OPEN,

src/os/unix/ngx_files.h

diff --git a/src/os/unix/ngx_files.h b/src/os/unix/ngx_files.h
index ccaf44a..f41eba5 100644
--- a/src/os/unix/ngx_files.h
+++ b/src/os/unix/ngx_files.h
@@ -64,6 +64,7 @@
 #define NGX_FILE_OPEN            0
 #define NGX_FILE_TRUNCATE        O_CREAT|O_TRUNC
 #define NGX_FILE_APPEND          O_WRONLY|O_APPEND
+#define NGX_FILE_NONBLOCK        O_NONBLOCK
 
 #define NGX_FILE_DEFAULT_ACCESS  0644
 #define NGX_FILE_OWNER_ACCESS    0600

src/os/win32/ngx_files.h

diff --git a/src/os/win32/ngx_files.h b/src/os/win32/ngx_files.h
index 610fcd0..c5bb888 100644
--- a/src/os/win32/ngx_files.h
+++ b/src/os/win32/ngx_files.h
@@ -64,6 +64,7 @@
 #define NGX_FILE_WRONLY             GENERIC_WRITE
 #define NGX_FILE_RDWR               GENERIC_READ|GENERIC_WRITE
 #define NGX_FILE_APPEND             FILE_APPEND_DATA|SYNCHRONIZE
+#define NGX_FILE_NONBLOCK           0
 
 #define NGX_FILE_CREATE_OR_OPEN     OPEN_ALWAYS
 #define NGX_FILE_OPEN               OPEN_EXISTING