POSIX_TRACE_CREATE(P) POSIX Programmer's Manual POSIX_TRACE_CREATE(P)NAME
posix_trace_create, posix_trace_create_withlog, posix_trace_flush,
posix_trace_shutdown - trace stream initialization, flush, and shutdown
from a process (TRACING)
SYNOPSIS
#include <sys/types.h>
#include <trace.h>
int posix_trace_create(pid_t pid,
const trace_attr_t *restrict attr,
trace_id_t *restrict trid);
int posix_trace_create_withlog(pid_t pid,
const trace_attr_t *restrict attr, int file_desc,
trace_id_t *restrict trid);
int posix_trace_flush(trace_id_t trid);
int posix_trace_shutdown(trace_id_t trid);
DESCRIPTION
The posix_trace_create() function shall create an active trace stream.
It allocates all the resources needed by the trace stream being created
for tracing the process specified by pid in accordance with the attr
argument. The attr argument represents the initial attributes of the
trace stream and shall have been initialized by the function
posix_trace_attr_init() prior to the posix_trace_create() call. If the
argument attr is NULL, the default attributes shall be used. The attr
attributes object shall be manipulated through a set of functions
described in the posix_trace_attr family of functions. If the
attributes of the object pointed to by attr are modified later, the
attributes of the trace stream shall not be affected. The creation-time
attribute of the newly created trace stream shall be set to the value
of the system clock, if the Timers option is not supported, or to the
value of the CLOCK_REALTIME clock, if the Timers option is supported.
The pid argument represents the target process to be traced. If the
process executing this function does not have appropriate privileges to
trace the process identified by pid, an error shall be returned. If the
pid argument is zero, the calling process shall be traced.
The posix_trace_create() function shall store the trace stream identi‐
fier of the new trace stream in the object pointed to by the trid argu‐
ment. This trace stream identifier shall be used in subsequent calls to
control tracing. The trid argument may only be used by the following
functions:
posix_trace_clear()posix_trace_getnext_event()posix_trace_eventid_equal()posix_trace_shutdown()posix_trace_eventid_get_name()posix_trace_start()posix_trace_eventtypelist_getnext_id()posix_trace_stop()posix_trace_eventtypelist_rewind()posix_trace_timedgetnext_event()posix_trace_get_attr()posix_trace_trid_eventid_open()posix_trace_get_status()posix_trace_trygetnext_event()
If the Trace Event Filter option is supported, the following additional
functions may use the trid argument:
posix_trace_get_filter()posix_trace_set_filter()
In particular, notice that the operations normally used by a trace ana‐
lyzer process, such as posix_trace_rewind() or posix_trace_close(),
cannot be invoked using the trace stream identifier returned by the
posix_trace_create() function.
A trace stream shall be created in a suspended state. If the Trace
Event Filter option is supported, its trace event type filter shall be
empty.
The posix_trace_create() function may be called multiple times from the
same or different processes, with the system-wide limit indicated by
the runtime invariant value {TRACE_SYS_MAX}, which has the minimum
value {_POSIX_TRACE_SYS_MAX}.
The trace stream identifier returned by the posix_trace_create() func‐
tion in the argument pointed to by trid is valid only in the process
that made the function call. If it is used from another process, that
is a child process, in functions defined in IEEE Std 1003.1-2001, these
functions shall return with the error [EINVAL].
The posix_trace_create_withlog() function shall be equivalent to
posix_trace_create(), except that it associates a trace log with this
stream. The file_desc argument shall be the file descriptor designating
the trace log destination. The function shall fail if this file
descriptor refers to a file with a file type that is not compatible
with the log policy associated with the trace log. The list of the
appropriate file types that are compatible with each log policy is
implementation-defined.
The posix_trace_create_withlog() function shall return in the parameter
pointed to by trid the trace stream identifier, which uniquely identi‐
fies the newly created trace stream, and shall be used in subsequent
calls to control tracing. The trid argument may only be used by the
following functions:
posix_trace_clear()posix_trace_getnext_event()posix_trace_eventid_equal()posix_trace_shutdown()posix_trace_eventid_get_name()posix_trace_start()posix_trace_eventtypelist_getnext_id()posix_trace_stop()posix_trace_eventtypelist_rewind()posix_trace_timedgetnext_event()posix_trace_flush()posix_trace_trid_eventid_open()posix_trace_get_attr()posix_trace_trygetnext_event()posix_trace_get_status()
If the Trace Event Filter option is supported, the following additional
functions may use the trid argument:
posix_trace_get_filter()posix_trace_set_filter()
In particular, notice that the operations normally used by a trace ana‐
lyzer process, such as posix_trace_rewind() or posix_trace_close(),
cannot be invoked using the trace stream identifier returned by the
posix_trace_create_withlog() function.
The posix_trace_flush() function shall initiate a flush operation which
copies the contents of the trace stream identified by the argument trid
into the trace log associated with the trace stream at the creation
time. If no trace log has been associated with the trace stream pointed
to by trid, this function shall return an error. The termination of the
flush operation can be polled by the posix_trace_get_status() function.
During the flush operation, it shall be possible to trace new trace
events up to the point when the trace stream becomes full. After flush‐
ing is completed, the space used by the flushed trace events shall be
available for tracing new trace events.
If flushing the trace stream causes the resulting trace log to become
full, the trace log full policy shall be applied. If the trace log-
full-policy attribute is set, the following occurs:
POSIX_TRACE_UNTIL_FULL
The trace events that have not yet been flushed shall be dis‐
carded.
POSIX_TRACE_LOOP
The trace events that have not yet been flushed shall be written
to the beginning of the trace log, overwriting previous trace
events stored there.
POSIX_TRACE_APPEND
The trace events that have not yet been flushed shall be
appended to the trace log.
The posix_trace_shutdown() function shall stop the tracing of trace
events in the trace stream identified by trid, as if posix_trace_stop()
had been invoked. The posix_trace_shutdown() function shall free all
the resources associated with the trace stream.
The posix_trace_shutdown() function shall not return until all the
resources associated with the trace stream have been freed. When the
posix_trace_shutdown() function returns, the trid argument becomes an
invalid trace stream identifier. A call to this function shall uncondi‐
tionally deallocate the resources regardless of whether all trace
events have been retrieved by the analyzer process. Any thread blocked
on one of the trace_getnext_event() functions (which specified this
trid) before this call is unblocked with the error [EINVAL].
If the process exits, invokes a member of the exec family of functions,
or is terminated, the trace streams that the process had created and
that have not yet been shut down, shall be automatically shut down as
if an explicit call were made to the posix_trace_shutdown() function.
For an active trace stream with log, when the posix_trace_shutdown()
function is called, all trace events that have not yet been flushed to
the trace log shall be flushed, as in the posix_trace_flush() function,
and the trace log shall be closed.
When a trace log is closed, all the information that may be retrieved
later from the trace log through the trace interface shall have been
written to the trace log. This information includes the trace
attributes, the list of trace event types (with the mapping between
trace event names and trace event type identifiers), and the trace sta‐
tus.
In addition, unspecified information shall be written to the trace log
to allow detection of a valid trace log during the posix_trace_open()
operation.
The posix_trace_shutdown() function shall not return until all trace
events have been flushed.
RETURN VALUE
Upon successful completion, these functions shall return a value of
zero. Otherwise, they shall return the corresponding error number.
The posix_trace_create() and posix_trace_create_withlog() functions
store the trace stream identifier value in the object pointed to by
trid, if successful.
ERRORS
The posix_trace_create() and posix_trace_create_withlog() functions
shall fail if:
EAGAIN No more trace streams can be started now. {TRACE_SYS_MAX} has
been exceeded.
EINTR The operation was interrupted by a signal. No trace stream was
created.
EINVAL One or more of the trace parameters specified by the attr param‐
eter is invalid.
ENOMEM The implementation does not currently have sufficient memory to
create the trace stream with the specified parameters.
EPERM The caller does not have appropriate privilege to trace the
process specified by pid.
ESRCH The pid argument does not refer to an existing process.
The posix_trace_create_withlog() function shall fail if:
EBADF The file_desc argument is not a valid file descriptor open for
writing.
EINVAL The file_desc argument refers to a file with a file type that
does not support the log policy associated with the trace log.
ENOSPC No space left on device. The device corresponding to the argu‐
ment file_desc does not contain the space required to create
this trace log.
The posix_trace_flush() and posix_trace_shutdown() functions shall
fail if:
EINVAL The value of the trid argument does not correspond to an active
trace stream with log.
EFBIG The trace log file has attempted to exceed an implementation-
defined maximum file size.
ENOSPC No space left on device.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOclock_getres() , exec() , posix_trace_attr_init() , posix_trace_clear()
, posix_trace_close() , posix_trace_eventid_equal() ,
posix_trace_eventtypelist_getnext_id() , posix_trace_flush() ,
posix_trace_get_attr() , posix_trace_get_filter() ,
posix_trace_get_status() , posix_trace_getnext_event() ,
posix_trace_open() , posix_trace_set_filter() , posix_trace_shutdown()
, posix_trace_start() , posix_trace_timedgetnext_event() ,
posix_trace_trid_eventid_open() , posix_trace_start() , time() , the
Base Definitions volume of IEEE Std 1003.1-2001, <sys/types.h>,
<trace.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 POSIX_TRACE_CREATE(P)
