Kernel Threads vs. CMA Threads (new)

The CMA threads (libcma) package, which is POSIX P1003.1a (Draft 4) compliant, is based on Concert Multi Thread Architecture (CMA). CMA is a user level threads package in which thread scheduling and synchronization are handled within the user space without the kernel's assistance.

CMA threads have been deprecated (slated for future obsolescence) at HP-UX 11i. This development environment will not be shipped in a future HP-UX release. Also, there is no plan to release native IA-64 CMA threads on IA-64 platforms. It is now strongly recommended that you use the currently supported kernel threads libraries and development tools. Thus, applications using CMA threads should start migrating to kernel threads.

Multi-threading is also supported in the HP-UX kernel at 11i and is known as kernel, POSIX or 1x1 threads. This kernel threads implementation, libpthread, is compliant with the approved POSIX 1003.1c (POSIX.1-1996 Draft 10) standard and will be replacing the CMA threads package.

The kernel threads implementation allows the application to take advantage of multiple processors in the system to parallelize execution of threads.

Compatibility Issues

It is expected that all existing CMA applications will continue to run on future releases.

As a POSIX standard, the kernel thread implementation facilitates better application portability on to POSIX-compliant vendor platforms. CMA applications may have to be ported to HP-UX POSIX threads in future releases, including those supporting IA-64, as there are differences in certain API's between CMA threads and HP-UX POSIX threads.

A white paper Porting CMA Threads Programs to HP-UX 11.0 POSIX Threads is available on the Web to help move from CMA threads to kernel threads (http://docs.hp.com). The HP-UX Software Transition Kit (STK) for 11.0/11.x/IA-64 is also available (http://devresource.hp.com/STK/) for assistance. The STK contains documents that explain how to perform a source code or system transition. For more information see http://devresource.hp.com/STK/toc_trans.html