Threads

Each command level has its own set of threads. These threads are suspended when a new level is entered and resumed when the owning level again becomes the current level. A thread that raises an error is not resumed unless explicitly restarted using the ,proceed command. In addition to any threads spawned by the user, each level has a thread that runs the command processor on that level. A new command-processor thread is started if the current one dies or is terminated. When a command level is abandoned for a lower level, or when a level is restarted using ,reset, all of the threads on that level are terminated and any dynamic-wind "after" thunks are run.

The following commands are useful when debugging multithreaded programs:

,resume [number]
Pops out to a given level and resumes running all threads at that level. Number defaults to zero.

,threads
Invokes the inspector on a list of the threads running at the next lower command level.

,exit-when-done [exp]
Waits until all user threads have completed and then exits back out to shell (or executive or whatever invoked Scheme 48 in the first place). Exp should evaluate to an integer which is then returned to the calling program.

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