The default thread library on Oracle Solaris 8 operating system is often referred to as the T1 library. This thread library implemented the m:n threading model, where m user threads are mapped to n kernel-level threads (LWPs). Oracle Solaris 8 operating system also shipped with an alternative and newer thread library in /usr/lib/lwp. The alternative thread library is often referred to as the T2 library, and it became the default thread library in Oracle Solaris 9 and 10 operating systems. In older releases of J2SE (pre-1.4.0 in particular) there were a number of issues with the default thread library (for example, bugs in the thread library, LWP synchronization problems, or LWP starvation). LWP starvation is a scenario in which there are user threads in the RUNNABLE state but there are no kernel level threads available.
Although the issues cited are historical, it should be noted that when the JDK software is deployed on Oracle Solaris 8 operating system, it still uses the T1 library by default. LWP starvation type issues do not arise because the JDK release uses "bound threads" so that each user thread is bound to a kernel thread. However in the event that you encounter an issue, such as a hang, which you believe is a thread library issue, then you can instruct the HotSpot VM to use the T2 library by adding /usr/lib/lwp to the LD_LIBRARY_PATH. To check if the T2 library is in use, issue the command pldd pid to list the libraries loaded by the specified process.
