Small cleanup/improvement to epoll creation

[David Lloyd]

On Tue, Apr 7, 2020 at 2:27 PM Alan Bateman <Alan.Bateman at oracle.com> wrote:
>
> On 06/04/2020 17:50, David Lloyd wrote:
> > Since glibc 2.9 (released at the end of 2008), there has been an
> > improved function for EPoll creation.  I would suggest the following
> > cleanup, which uses the "epoll_create1" function to set the FD to
> > close-on-exec (which is generally just good practice AFAICT, even if
> > it's not exactly one that has been universally adopted by OpenJDK thus
> > far).
> This looks okay, just need to update the exception message too.

Ah yes, I missed that.

> You are right that we don't use CLOEXEC consistently. The JDK gets away due to
> heroics in Process code to ensure that file descriptors are closed.

I seem to recall quite a lot of discussion on this... heroics is
exactly the right word :)

diff --git a/src/java.base/linux/native/libnio/ch/EPoll.c
b/src/java.base/linux/native/libnio/ch/EPoll.c
index 2100de5f215..f41fb49c405 100644
--- a/src/java.base/linux/native/libnio/ch/EPoll.c
+++ b/src/java.base/linux/native/libnio/ch/EPoll.c
@@ -57,10 +57,9 @@ Java_sun_nio_ch_EPoll_dataOffset(JNIEnv* env, jclass clazz)

 JNIEXPORT jint JNICALL
 Java_sun_nio_ch_EPoll_create(JNIEnv *env, jclass clazz) {
-    /* size hint not used in modern kernels */
-    int epfd = epoll_create(256);
+    int epfd = epoll_create1(EPOLL_CLOEXEC);
     if (epfd < 0) {
-        JNU_ThrowIOExceptionWithLastError(env, "epoll_create failed");
+        JNU_ThrowIOExceptionWithLastError(env, "epoll_create1 failed");
     }
     return epfd;
 }


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