When a breakpoint is encountered and the process-level debug agent pdebug is in control, the process being debugged and all its threads are stopped. All other processes continue to run and interrupts remain enabled.
When the process's threads are stopped and the debugger is in control, you may examine the state of any thread within the process. For more info on examining thread states, see the gdb docs.
The pdebug agent may either be included in the image and started in the image startup script or started later from any available filesystem that contains pdebug. The pdebug command-line invocation specifies which device is used.
You can start pdebug in one of three ways, reflecting the nature of the connection between the debugger and the debug agent: