6850720: Allow POSIX_SPAWN to be used for ProcessImpl on Linux

[David Lloyd]

I've submitted a bug report via bugreport.java.com.  If/when it gets
promoted to a proper JIRA with an issue number, I'll see if I can put
the patch up on jdk/submit.
On Thu, Oct 18, 2018 at 4:42 PM David Lloyd <david.lloyd at redhat.com> wrote:
>
> The issue 6850720 isn't _exactly_ to use POSIX_SPAWN for process
> launching on Linux, but it's the closest I could find out of what are
> really a surprisingly large number of issues that refer to posix_spawn
> in one way or another relating to ProcessImpl.  There's a different
> issue to move from vfork to posix_spawn on Solaris, but I wasn't sure
> if that one was quite right to hang this off of.  Maybe it should be
> yet another issue of its own.
>
> Anyway: this is a follow-up to the email thread entitled "Runtime.exec
> : vfork() concerns and a fix proposal", where it was casually
> mentioned that maybe posix_spawn could become an option on Linux,
> whereafter it could be thoroughly tested by brave individuals and
> eventually maybe become the default on that platform, obsoleting the
> vfork support for good.
>
> The following patch does just that.  I've tested it launching a
> multi-process WildFly instance a bunch of times, in conjunction with
> the conveniently existent "jdk.lang.Process.launchMechanism" property,
> and nothing exploded so here it is.  The usual deal with git patches:
> apply directly through "patch -p1".
>
> commit f0eb9ff7c46dff76f91160491fcca0eb25d0ab95
> Author: David M. Lloyd <david.lloyd at redhat.com>
> Date:   Thu Oct 18 15:56:37 2018 -0500
>
>     [JDK-6850720] Enable POSIX_SPAWN as an option for child process
> creation on Linux
>
> diff --git a/make/launcher/Launcher-java.base.gmk
> b/make/launcher/Launcher-java.base.gmk
> index 0ce0287d2be..c28fe42d102 100644
> --- a/make/launcher/Launcher-java.base.gmk
> +++ b/make/launcher/Launcher-java.base.gmk
> @@ -84,7 +84,7 @@ endif
>
>  ################################################################################
>
> -ifneq ($(findstring $(OPENJDK_TARGET_OS), macosx solaris aix), )
> +ifneq ($(findstring $(OPENJDK_TARGET_OS), macosx solaris aix linux), )
>    $(eval $(call SetupJdkExecutable, BUILD_JSPAWNHELPER, \
>        NAME := jspawnhelper, \
>        SRC := $(TOPDIR)/src/$(MODULE)/unix/native/jspawnhelper, \
> diff --git a/src/java.base/unix/classes/java/lang/ProcessImpl.java
> b/src/java.base/unix/classes/java/lang/ProcessImpl.java
> index 368a4f7380b..959e50dfecd 100644
> --- a/src/java.base/unix/classes/java/lang/ProcessImpl.java
> +++ b/src/java.base/unix/classes/java/lang/ProcessImpl.java
> @@ -89,7 +89,7 @@ final class ProcessImpl extends Process {
>
>      private static enum Platform {
>
> -        LINUX(LaunchMechanism.VFORK, LaunchMechanism.FORK),
> +        LINUX(LaunchMechanism.VFORK, LaunchMechanism.POSIX_SPAWN,
> LaunchMechanism.FORK),
>
>          BSD(LaunchMechanism.POSIX_SPAWN, LaunchMechanism.FORK),
>
> diff --git a/src/java.base/unix/native/libjava/ProcessImpl_md.c
> b/src/java.base/unix/native/libjava/ProcessImpl_md.c
> index 533584fdb7a..6869a64f2cc 100644
> --- a/src/java.base/unix/native/libjava/ProcessImpl_md.c
> +++ b/src/java.base/unix/native/libjava/ProcessImpl_md.c
> @@ -44,7 +44,7 @@
>  #include <signal.h>
>  #include <string.h>
>
> -#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> +#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> || defined(__linux__)
>  #include <spawn.h>
>  #endif
>
> @@ -390,7 +390,7 @@ forkChild(ChildStuff *c) {
>      return resultPid;
>  }
>
> -#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> +#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> || defined(__linux__)
>  static pid_t
>  spawnChild(JNIEnv *env, jobject process, ChildStuff *c, const char
> *helperpath) {
>      pid_t resultPid;
> @@ -489,7 +489,7 @@ startChild(JNIEnv *env, jobject process,
> ChildStuff *c, const char *helperpath)
>  #endif
>        case MODE_FORK:
>          return forkChild(c);
> -#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> +#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)
> || defined(__linux__)
>        case MODE_POSIX_SPAWN:
>          return spawnChild(env, process, c, helperpath);
>  #endif



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