[nginx] Events: use eventfd() instead of syscall(SYS_eventfd) if...

[Ruslan Ermilov]

details:   http://hg.nginx.org/nginx/rev/31dd63dcb9ea
branches:  
changeset: 5707:31dd63dcb9ea
user:      Ruslan Ermilov <ru at nginx.com>
date:      Fri May 23 16:37:05 2014 +0400
description:
Events: use eventfd() instead of syscall(SYS_eventfd) if possible.

This fixes --with-file-aio support on systems that lack eventfd()
syscall, notably aarch64 Linux.

The syscall(SYS_eventfd) may still be necessary on systems that
have eventfd() syscall in the kernel but lack it in glibc, e.g.
as seen in the current CentOS 5 release.

diffstat:

 auto/unix                            |  33 +++++++++++++++++++++++++++------
 src/event/modules/ngx_epoll_module.c |   8 ++++----
 src/os/unix/ngx_linux_config.h       |   3 +++
 3 files changed, 34 insertions(+), 10 deletions(-)

diffs (103 lines):

diff -r a2bf26774cd3 -r 31dd63dcb9ea auto/unix
--- a/auto/unix	Fri May 23 13:47:05 2014 +0400
+++ b/auto/unix	Fri May 23 16:37:05 2014 +0400
@@ -398,16 +398,36 @@ if [ $NGX_FILE_AIO = YES ]; then
 
     if [ $ngx_found = yes ]; then
         CORE_SRCS="$CORE_SRCS $FILE_AIO_SRCS"
+    fi
 
-    elif [ $ngx_found = no ]; then
+    if [ $ngx_found = no ]; then
 
         ngx_feature="Linux AIO support"
         ngx_feature_name="NGX_HAVE_FILE_AIO"
         ngx_feature_run=no
         ngx_feature_incs="#include <linux/aio_abi.h>
-                          #include <sys/syscall.h>"
+                          #include <sys/eventfd.h>"
         ngx_feature_path=
         ngx_feature_libs=
+        ngx_feature_test="struct iocb  iocb;
+                          iocb.aio_lio_opcode = IOCB_CMD_PREAD;
+                          iocb.aio_flags = IOCB_FLAG_RESFD;
+                          iocb.aio_resfd = -1;
+                          (void) eventfd(0, 0)"
+        . auto/feature
+
+        if [ $ngx_found = yes ]; then
+            have=NGX_HAVE_EVENTFD . auto/have
+            have=NGX_HAVE_SYS_EVENTFD_H . auto/have
+            CORE_SRCS="$CORE_SRCS $LINUX_AIO_SRCS"
+        fi
+    fi
+
+    if [ $ngx_found = no ]; then
+
+        ngx_feature="Linux AIO support (SYS_eventfd)"
+        ngx_feature_incs="#include <linux/aio_abi.h>
+                          #include <sys/syscall.h>"
         ngx_feature_test="int  n = SYS_eventfd;
                           struct iocb  iocb;
                           iocb.aio_lio_opcode = IOCB_CMD_PREAD;
@@ -418,16 +438,17 @@ if [ $NGX_FILE_AIO = YES ]; then
         if [ $ngx_found = yes ]; then
             have=NGX_HAVE_EVENTFD . auto/have
             CORE_SRCS="$CORE_SRCS $LINUX_AIO_SRCS"
+        fi
+    fi
 
-        else
-            cat << END
+    if [ $ngx_found = no ]; then
+        cat << END
 
 $0: no supported file AIO was found
 Currently file AIO is supported on FreeBSD 4.3+ and Linux 2.6.22+ only
 
 END
-           exit 1
-        fi
+        exit 1
     fi
 fi
 
diff -r a2bf26774cd3 -r 31dd63dcb9ea src/event/modules/ngx_epoll_module.c
--- a/src/event/modules/ngx_epoll_module.c	Fri May 23 13:47:05 2014 +0400
+++ b/src/event/modules/ngx_epoll_module.c	Fri May 23 16:37:05 2014 +0400
@@ -193,10 +193,6 @@ ngx_module_t  ngx_epoll_module = {
  * We call io_setup(), io_destroy() io_submit(), and io_getevents() directly
  * as syscalls instead of libaio usage, because the library header file
  * supports eventfd() since 0.3.107 version only.
- *
- * Also we do not use eventfd() in glibc, because glibc supports it
- * since 2.8 version and glibc maps two syscalls eventfd() and eventfd2()
- * into single eventfd() function with different number of parameters.
  */
 
 static int
@@ -227,7 +223,11 @@ ngx_epoll_aio_init(ngx_cycle_t *cycle, n
     int                 n;
     struct epoll_event  ee;
 
+#if (NGX_HAVE_SYS_EVENTFD_H)
+    ngx_eventfd = eventfd(0, 0);
+#else
     ngx_eventfd = syscall(SYS_eventfd, 0);
+#endif
 
     if (ngx_eventfd == -1) {
         ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
diff -r a2bf26774cd3 -r 31dd63dcb9ea src/os/unix/ngx_linux_config.h
--- a/src/os/unix/ngx_linux_config.h	Fri May 23 13:47:05 2014 +0400
+++ b/src/os/unix/ngx_linux_config.h	Fri May 23 16:37:05 2014 +0400
@@ -94,6 +94,9 @@ extern ssize_t sendfile(int s, int fd, i
 
 
 #if (NGX_HAVE_FILE_AIO)
+#if (NGX_HAVE_SYS_EVENTFD_H)
+#include <sys/eventfd.h>
+#endif
 #include <sys/syscall.h>
 #include <linux/aio_abi.h>
 typedef struct iocb  ngx_aiocb_t;