'\"macro stdmacro
.\"
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.TH PMLOOKUPIPC 3 "PCP" "Performance Co-Pilot"
.SH NAME
\f3__pmOverrideLastFd\f1,
\f3__pmPrintIPC\f1,
\f3__pmResetIPC\f1 \- IPC version infrastructure support
.SH "C SYNOPSIS"
.ft 3
#include "pmapi.h"
.br
#include "libpcp.h"
.sp
void __pmOverrideLastFd(int \fIfd\fP);
.br
void __pmPrintIPC(void);
.br
void __pmResetIPC(int \fIfd\fP);
.sp
cc ... \-lpcp
.ft 1
.SH CAVEAT
This documentation is intended for internal Performance Co-Pilot
(PCP) developer use.
.PP
These interfaces are not part of the PCP APIs that are guaranteed to
remain fixed across releases, and they may not work, or may provide
different semantics at some point in the future.
.SH DESCRIPTION
IPC channels throughout the distributed PCP framework are affected by the
PCP 2.0 (and later) PDU changes.  These functions are the interface to the libpcp IPC
connection management global data.  This data consists of a hash table of
__pmIPC structures (indexed by file descriptor) and a cached, most-recently-used
file descriptor.
.PP
The
.B __pmOverrideLastFd
is an escape mechanism for use in those situations where the last PDU
fetch did not go through the usual channels (i.e. __pmGetPDU), so as to ensure
that the cached file descriptor is the correct file descriptor for the PDU
which is currently being processed.  This will typically be used for archive
PDU processing or where version information is not available for a given file
descriptor (e.g. immediately prior to a PDU version exchange).
.PP
.B __pmPrintIPC
is a useful debugging routine for displaying a table mapping all currently
registered file descriptors to their associated PDU version numbers.  Unused
entries in this table should display the value zero in the version column.
.PP
.B __pmResetIPC
resets the version information associated with the given file descriptor to some
known (invalid) number.  Subsequent lookups on this file descriptor will return
an UNKNOWN_VERSION embedded within the __pmIPC structure.
.SH DIAGNOSTICS
A negative return value from \f3__pmOverrideLastFd\f1 indicates that the
file descriptor argument is not registered in the hash table.
This typically indicates closure of an IPC channel, so PM_ERR_IPC is returned
if this is the case.
.SH SEE ALSO
.BR PMAPI (3)