> I have a code that has several probes with the same probename. When I define
> the probe to use a translator and then try to match for all the occurances of
> the probename in a D script I get the following error:
>
> dtrace: invalid probe specifier mpi__test$target:::RECV_REQ_ACT_EV {
> printf("%d %d", args[0]->bar, args[0]->baz); }: in action list: args[ ] may
> not be referenced because probe description mpi__test9055:::RECV_REQ_ACT_EV
> matches an unstable set of probes
>
> However if I specify the function the probe exists in things work fine. Like
> so,
>
> dtrace -c main -n 'mpi__test$target::recv_1:RECV_REQ_ACT_EV { printf("%d %d",
> args[0]->bar, args[0]->baz); }'
> dtrace: description 'mpi__test$target::recv_1:RECV_REQ_ACT_EV ' matched 1
> probe
> dtrace: pid 9057 has exited
> CPU ID FUNCTION:NAME
> 0 43963 recv_1:RECV_REQ_ACT_EV 1 2
>
> My question is there a way that if these two probes with the same
> probename can be defined such that the failing case would work? The
> reason I want to do this is in the case of MPI the probenames are
> Events and the certain events can be triggered in multiple places in
> the code. I'd also would like to avoid requiring D script writers to
> have to explicitly state which functions the probenames occur because I
> could see this possibly changing with time.
If you have multiple instrumentation sites for the probe RECV_REQ_ACT_EV,
and you want to allow people to instrument using the description:
mpi__test$target:::RECV_REQ_ACT_EV
independent of function and module (which is a good thing), then you need
to do two things:
(a) Ensure that all RECV_REQ_ACT_EV sites pass the same arguments to
the DTRACE_* macros that mark the probe locations, and
(b) Establish the appropriate provider stability, which is done by
#pragma D attributes after the provider foo { } declaration.
Here is an example set of declarations from plockstat in libc:
#pragma D attributes Evolving/Evolving/ISA provider plockstat provider
#pragma D attributes Private/Private/Unknown provider plockstat module
#pragma D attributes Private/Private/Unknown provider plockstat function
#pragma D attributes Evolving/Evolving/ISA provider plockstat name
#pragma D attributes Evolving/Evolving/ISA provider plockstat args
which is probably similar to what you want. Notice that module are
function are marked Private, whereas the other items are Evolving
(i.e. mpi__test$target:::RECV_REQ_ACT_EV is a committed interface,
whereas mpi__test$target::some_function_name:RECV_REQ_ACT_EV is not)
The rule for args[] and translators when the clause matches more than one
probe is that args[] and translators will *not* be available if either of
the following conditions is true:
1. The Arguments Data stability of the matched provider is less than Evolving.
2. Any description component that is at least Evolving is empty or is
specified using a globbing expression.
These rules imply that providers that provide Evolving or better Arguments Data
stability must guarantee that all probes with identical field names in a field
of Evolving or better Name stability have identical argument signatures.
-Mike
--
Mike Shapiro, Solaris Kernel Development. blogs.sun.com/mws/
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