TotalView Users Guide - CI Wiki

Setting Breakpoints and Barriers
About Barrier Breakpoint States
Processes and threads at a barrier point are held or stopped, as follows:
Held A held process or thread cannot execute until all the
processes or threads in its group are at the barrier, or
until you manually release it. The various go and step
commands from the Group, Process, and Thread menus
cannot start held processes.
Stopped When all processes in the group reach a barrier point,
TotalView automatically releases them. They remain
stopped at the barrier point until you tell them to resume
executing.
You can manually release held processes and threads with the Hold and
Release commands found in the Group, Process, and Thread menus. When
you manually release a process, the go and step commands become available
again.
CLI: dfocus ... dhold
dfocus ... dunhold
You can reuse the Hold command to again toggle the hold state of the process
or thread. See “Holding and Releasing Processes and Threads” on page 231
for more information.
When a process or a thread is held, TotalView displays an H (for a held process)
or an h (for a held thread) in the process’s or thread’s entry in the Root
Window.
Setting a Barrier Breakpoint
You can set a barrier breakpoint by using the Action Point > Set Barrier
command or from the Action Point > Properties Dialog Box. As an alternative,
you can right-click on the line. From the displayed context menu, you
can select the Set Barrier command. (See Figure 235 on page 364.)
You most often use barrier points to synchronize a set of threads. When a
thread reaches a barrier, it stops, just as it does for a breakpoint. The difference
is that TotalView prevents—that is, holds—each thread reaching the
barrier from responding to resume commands (for example, step, next, or go)
until all threads in the affected set arrive at the barrier. When all threads
reach the barrier, TotalView considers the barrier to be satisfied and releases
all of the threads being held there. They are just released; they are not continued.
That is, they are left stopped at the barrier. If you continue the process,
those threads also run.
If you stop a process and then continue it, the held threads, including the
ones waiting at an unsatisfied barrier, do not run. Only unheld threads run.
TotalView Users Guide: version 8.7 363