DESCRIPTION
Errors that occur during pass 5 (execution) can have a variety of causes.
- exceptional events during script execution
-
The systemtap translator and runtime include numerous error checks
that aim to protect the systems and the users from mistakes or
transient conditions. The script may deliberately call the
error()
tapset function to signal a problem. Some memory needed for
accessing
$context
variables may be temporarily unavailable. Consider using the
try/catch
construct to wrap script fragments in exception-handling code.
Consider using the
stap --suppress-handler-errors
or
stap --skip-badvars
option.
- resource exhaustion
-
One of several types of space or time resource limits may be
exceeded by the script, including system overload, too many tuples
to be stored in an array, etc. Some of the error messages identify
the constraint by macro name, which may be individually raised.
Consider using the
stap --suppress-handler-errors
and/or
stap -g --suppress-time-limits
options. Extend or disable individual resource limits using the
stap -DSOME_LIMIT=NNNN
option.
- remote execution server problems
-
If you use the
stap --remote
option to direct a systemtap script to be executed somewhere else,
ensure that an SSH connection may be made to the remote host, and
that it has the current systemtap runtime installed & available.
- installation/permission problems
-
It is possible that your installation of systemtap was not correctly
installed. For example, the
/usr/bin/staprun
program may lack the necessary setuid permissions, or your invoking
userid might not have sufficient privileges (root, or
stapusr
and related group memberships). Environment
variables may interfere with locating
/usr/libexec/.../stapio.
- errors from target program
-
The program invoked by the
stap -c CMD
option may exit with a non-zero code.
- uncaught exceptions in the target program
-
When using
--runtime=dyninst
you may encounter an issue where the target program aborts with a
message like "terminate called after throwing an instance
of 'foo_exception'". This is unfortunately a limitation of Dyninst,
which sometimes prevents exceptions from properly unwinding through
instrumented code.
GATHERING MORE INFORMATION
Increasing the verbosity of pass-5 with an option such as --vp 00001 can help pinpoint the problem.