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On the value of static tracepoints

On the value of static tracepoints

Posted Apr 28, 2009 18:13 UTC (Tue) by fuhchee (subscriber, #40059)
In reply to: On the value of static tracepoints by michaeljt
Parent article: On the value of static tracepoints

> It might help if the user space APIs for accessing static tracepoints were
> able to fail with something equivalent to "tracepoint no longer available",
> and this was clearly documented

It's not an API in the sense of a programming interface, but the way
systemtap exposes tracepoints (and indeed any other event source such
as kprobes, utrace events, timers, ....), is that an attempt to attach
to a facility that does not exist/match results in just such an error
message.

Systemtap also has some facilities to adapt to changes in kernels and
elsewhere, using both a preprocessor construct (similar to a #if
KERNEL_VERSION), and a syntax to specify a list of alternative sources
of the same events (the "?" and "!" operators in a probe point sequence).

So systemtap's use of tracepoints in no way imposes a requirement that
they be unmodified and permanent.


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