A licensee and their customer think signal handlers in JVM should save and
restore errno. Otherwise, errno might be overwritten by signal handler.

A native method in customer application call msgrcv().
When the return value of msgrcv() is -1, errno is set to ECHILD.
The OS team in the licensee says,
"When some signal interruption occurs and the signal handler re-writes errno,
 such situation might occur."

They look into the source code of signal handler in JVM and find out the following
portion.

=====
.......
JVM_handle_linux_signal(int sig,
             siginfo_t* info,
             void* ucVoid,
             int abort_if_unrecognized)
{
  ucontext_t* uc = (ucontext_t*) ucVoid;

  if (sig == SIGCHLD) {
    // cleanup zombie pid for child thread
    ::waitpid(-1, 0, WNOHANG);
    return 1;
  }
.....
======

There seems a possibility that errno is replaced by ECHILD in waitpid.
Our customer believes that signal handlers should save errno and restore
on return.
The above example is waitpid/ECHILD case.
They think also errno may be overwritten in other system calls.

(Please read comment section also. There are more specific resuests from the licensee.)