What's new

• November 16th 1998: JDK 1.1.6 v2 completed
• August 17th 1998: JDK 1.1.6 completed.
• July 1998: Java For Linux Announced

Our JDK port is based from Javasoft sources; it uses Linux native threads as implemented by the LinuxThreads library. Therefore it will only run on i386-based Linux systems that support this library.

Features

• This port is based on the JDK 1.1.6.
• Threads are scheduled according to the Linux timesharing policy.
• Since the LinuxThreads library does not support priorities for the timesharing policies, Java priorities are ignored. This is valid with respect to the Java Language Specification.
• Since multithreaded programs cannot dump valid core files, the JVM enters infinite loops in case of problems. Use the kill command to delete all the threads.
• A few bugs have been fixed in Motif 2.1 during this port. This is the reason why this port is statically linked with Motif.
• This release has not been completely tailored for Linux. For instance, you should think about retrieving the font.properties file from the Java-Linux porting project.
• It is not easy to determine the size of the elements added to a window by a window manager. For this release, they are set by default to 25 for the top (title+border) and 5 for the three other borders. However, the user can adapt them to the window manager being used with the following environment variables : AWT_TOP_OFFSET, AWT_LEFT_OFFSET, AWT_BOTTOM_OFFSET and AWT_RIGHT_OFFSET.

System Requirements

This i386 port has been compiled and tested on a uniprocessor machine running a RedHat 5.0 Linux system upgraded with official RedHat RPMs. It seems to work properly on more recent RedHat versions.

The glibc-2.0.7-6, or later, should be installed, together with its related RPMs:

• amd-920824upl102-11
• glibc-2.0.7-6
• glibc-debug-2.0.7-6
• glibc-devel-2.0.7-6
• glibc-profile-2.0.7-6
• portmap-4.0-8
• texinfo-3.12-1
• ypbind-3.3-2

Note that the release has not been fully tested with more recent versions of RedHat or the glibc. In case of problems, consult the list of all the RPMs installed on the test machine.

Native threads

In order to get the JDK using Linux native threads, we have also developed freely available enhancements and proposals to improve support of LinuxThreads-based applications:

• It is possible to use an enhanced gdb with this port and to obtain the C stack of all the threads. This GDB enhancement is useful for debugging multithreaded applications.
• Kernel patch proposal to fix dynamic debugger attachment bugs.
• Kernel enhancement proposal for multithread-relative scheduling priorities (not ready yet).

Threads are then easier to debug since both Java and C debuggers can be used.

However, Java programs may fail if their authors have made false assumptions about the scheduling policy (the Java Language Specification is lax about thread rescheduling). They are usually stressed by implementations based on round-robin or timesharing policies, and even more with this port since Java priorities are not taken into account.

In addition, there is a small performance loss for Java programs which use synchronization extensively since locking is a bit more expensive with native threads. On the other hand, native thread ports are not stopped by page faults due to swap out and should be more efficient

Documentation

Please read the FAQ and the list of known bugs.

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