ERROR::FAULT(7stap)                                      ERROR::FAULT(7stap)

NAME         top

       error::fault - memory access faults

DESCRIPTION         top

       Read or write faults can occur during the operation of a systemtap
       script, if the script causes dereferencing of a pointer that turns
       out to be invalid.  This can be caused by using context variables
       that do not happen to have valid values, or perhaps references to
       memory that is unavailable at that moment due to paging.

       These fault conditions are benign because they are caught by the
       systemtap runtime, which cleanly terminates the script.  If quick
       termination is not desired, consider using the --skip-badvars or
       --suppress-handler-errors or -DMAXERRORS=NN stap options, or wrapping
       relevant parts of the probe handlers in a try/catch block.

       It may be possible to adjust the target program, to make it more
       likely that needed context variables are paged in when systemtap
       looks for them.  Consider adding some lightweight processing on the
       key variables, like a strlen(foo) for a string, or iterating across
       elements of an array or linked list, or touching a few bytes of a
       heap-allocated block.  The idea is to trigger any page faults in the
       target program, before systemtap would need to (but can't).

SEE ALSO         top


COLOPHON         top

       This page is part of the systemtap (a tracing and live-system
       analysis tool) project.  Information about the project can be found
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