Function JVM_handle_linux_signal() is hidden in 1.4.2-beta:

raq:~> strings libjvm.so | grep beta
1.4.2-beta-b19
raq:~> nm -D libjvm.so | grep JVM_handle_linux_signal
raq:~> 

This function is public before 1.4.2, for example, with 1.4.1:

[huanghui@raq client]$ strings libjvm.so|grep "1.4.1-"
1.4.1-b21
[huanghui@raq client]$ nm -D libjvm.so|grep JVM_handle_linux_signal
0029df90 T JVM_handle_linux_signal

This can cause applications to fail if they follow our suggestion
on how to install their own signal handlers and chain JVM signal
handler, because they won't be able to call JVM_handle_linux_signal().
The technique is discussed here:

 http://developer.java.sun.com/developer/bugParade/bugs/4361067.html