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tnfctl_internal_open - create handle for internal process probe control

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



tnfctl_errcode_t tnfctl_internal_open(tnfctl_handle_t **ret_val);

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.

tnfctl_internal_open() returns TNFCTL_ERR_NONE upon success.

TNFCTL_ERR_ALLOCFAIL TNFCTL_ERR_BUSY TNFCTL_ERR_NOLIBTNFPROBE TNFCTL_ERR_INTERNAL

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

ATTRIBUTE TYPE ATTRIBUTE VALUE

MT Level MT-Safe

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

Linker and Libraries Guide

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.