Types of Restartable Processes

Processes do not explicitly declare themselves restartable, that is, there is no function call to declare a process restartable at the start of its main() program. Instead, a process can be run as a restartable process. Specifically, a process can be run as either a direct or indirect restartable process:

• Direct restartable processes are loaded and run using the C_INIT command arun with the -g option.

• Indirect restartable processes are spawned from restartable processes using the hrfexec(2RESTART) family of API calls. hrfexec() calls operate in a similar manner to afexec() calls, but provide an additional PmmName parameter. The PmmName parameter is used to identify the calls used for the purposes of process restart:

  #include <hr/hr.h> 
  int hrfexecve( PmmName *       baseName,
                 const char *    path,
                 KnCap *         cprocesscap,
                 const AcParam * param,
                 char const *    argv,
                 char const *    envp);
  (...)

The distinction between direct and indirect processes is important in understanding the automatic restart mechanism provided by the Hot Restart Controller. When an error occurs, the Hot Restart Controller first stops all processes in the group. After the processes are stopped, only the direct restartable processes will be restarted. These processes (re-executed from their initial entry point) are responsible for restarting any indirect processes they may have spawned.