TNFCTL_INTERNAL_OPEN(3TNF) TNF Library Functions TNFCTL_INTERNAL_OPEN(3TNF)


NAME


tnfctl_internal_open - create handle for internal process probe control

SYNOPSIS


cc [ flag ... ] file ... -ltnfctl [ library ... ]
#include <tnf/tnfctl.h>


tnfctl_errcode_t tnfctl_internal_open(tnfctl_handle_t **ret_val);


DESCRIPTION


tnfctl_internal_open() returns in ret_val a pointer to an opaque handle
that can be used to control probes in the same process as the caller
(internal process probe control). The process must have libtnfprobe.so.1
loaded. Probes in libraries that are brought in by dlopen(3C) will be
visible after the library has been opened. Probes in libraries closed by
a dlclose(3C) will not be visible after the library has been
disassociated. See the NOTES section for more details.

RETURN VALUES


tnfctl_internal_open() returns TNFCTL_ERR_NONE upon success.

ERRORS


TNFCTL_ERR_ALLOCFAIL
A memory allocation failure occurred.


TNFCTL_ERR_BUSY
Another client is already tracing this
program (internally or externally).


TNFCTL_ERR_NOLIBTNFPROBE
libtnfprobe.so.1 is not linked in the target
process.


TNFCTL_ERR_INTERNAL
An internal error occurred.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT Level | MT-Safe |
+---------------+-----------------+

SEE ALSO


ld(1), prex(1), TNF_PROBE(3TNF), dlopen(3C), dlclose(3C),
libtnfctl(3TNF), tracing(3TNF), attributes(5)


Linker and Libraries Guide

NOTES


libtnfctl interposes on dlopen(3C) and dlclose(3C) in order to be
notified of libraries being dynamically opened and closed. This
interposition is necessary for internal process probe control to update
its list of probes. In these interposition functions, a lock is acquired
to synchronize on traversal of the library list maintained by the runtime
linker. To avoid deadlocking on this lock, tnfctl_internal_open() should
not be called from within the init section of a library that can be
opened by dlopen(3C).


Since interposition does not work as expected when a library is opened
dynamically, tnfctl_internal_open() should not be used if the client
opened libtnfctl through dlopen(3C). In this case, the client program
should be built with a static dependency on libtnfctl. Also, if the
client program is explicitly linking in -ldl, it should link -ltnfctl
before -ldl.


Probes in filtered libraries (see ld(1)) will not be seen because the
filtee (backing library) is loaded lazily on the first symbol reference
and not at process startup or dlopen(3C) time. A workaround is to call
tnfctl_check_libs(3TNF) once the caller is sure that the filtee has been
loaded.


March 1, 2004 TNFCTL_INTERNAL_OPEN(3TNF)