mirror of https://gitee.com/openkylin/linux.git
154 lines
5.4 KiB
Plaintext
154 lines
5.4 KiB
Plaintext
libtraceevent(3)
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================
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NAME
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----
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tep_register_comm, tep_override_comm, tep_pid_is_registered,
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tep_data_comm_from_pid, tep_data_pid_from_comm, tep_cmdline_pid -
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Manage pid to process name mappings.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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int *tep_register_comm*(struct tep_handle pass:[*]_tep_, const char pass:[*]_comm_, int _pid_);
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int *tep_override_comm*(struct tep_handle pass:[*]_tep_, const char pass:[*]_comm_, int _pid_);
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bool *tep_is_pid_registered*(struct tep_handle pass:[*]_tep_, int _pid_);
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const char pass:[*]*tep_data_comm_from_pid*(struct tep_handle pass:[*]_pevent_, int _pid_);
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struct cmdline pass:[*]*tep_data_pid_from_comm*(struct tep_handle pass:[*]_pevent_, const char pass:[*]_comm_, struct cmdline pass:[*]_next_);
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int *tep_cmdline_pid*(struct tep_handle pass:[*]_pevent_, struct cmdline pass:[*]_cmdline_);
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--
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DESCRIPTION
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-----------
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These functions can be used to handle the mapping between pid and process name.
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The library builds a cache of these mappings, which is used to display the name
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of the process, instead of its pid. This information can be retrieved from
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tracefs/saved_cmdlines file.
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The _tep_register_comm()_ function registers a _pid_ / process name mapping.
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If a command with the same _pid_ is already registered, an error is returned.
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The _pid_ argument is the process ID, the _comm_ argument is the process name,
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_tep_ is the event context. The _comm_ is duplicated internally.
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The _tep_override_comm()_ function registers a _pid_ / process name mapping.
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If a process with the same pid is already registered, the process name string is
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udapted with the new one. The _pid_ argument is the process ID, the _comm_
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argument is the process name, _tep_ is the event context. The _comm_ is
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duplicated internally.
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The _tep_is_pid_registered()_ function checks if a pid has a process name
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mapping registered. The _pid_ argument is the process ID, _tep_ is the event
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context.
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The _tep_data_comm_from_pid()_ function returns the process name for a given
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pid. The _pid_ argument is the process ID, _tep_ is the event context.
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The returned string should not be freed, but will be freed when the _tep_
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handler is closed.
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The _tep_data_pid_from_comm()_ function returns a pid for a given process name.
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The _comm_ argument is the process name, _tep_ is the event context.
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The argument _next_ is the cmdline structure to search for the next pid.
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As there may be more than one pid for a given process, the result of this call
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can be passed back into a recurring call in the _next_ parameter, to search for
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the next pid. If _next_ is NULL, it will return the first pid associated with
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the _comm_. The function performs a linear search, so it may be slow.
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The _tep_cmdline_pid()_ function returns the pid associated with a given
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_cmdline_. The _tep_ argument is the event context.
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RETURN VALUE
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------------
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_tep_register_comm()_ function returns 0 on success. In case of an error -1 is
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returned and errno is set to indicate the cause of the problem: ENOMEM, if there
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is not enough memory to duplicate the _comm_ or EEXIST if a mapping for this
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_pid_ is already registered.
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_tep_override_comm()_ function returns 0 on success. In case of an error -1 is
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returned and errno is set to indicate the cause of the problem: ENOMEM, if there
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is not enough memory to duplicate the _comm_.
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_tep_is_pid_registered()_ function returns true if the _pid_ has a process name
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mapped to it, false otherwise.
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_tep_data_comm_from_pid()_ function returns the process name as string, or the
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string "<...>" if there is no mapping for the given pid.
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_tep_data_pid_from_comm()_ function returns a pointer to a struct cmdline, that
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holds a pid for a given process, or NULL if none is found. This result can be
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passed back into a recurring call as the _next_ parameter of the function.
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_tep_cmdline_pid()_ functions returns the pid for the give cmdline. If _cmdline_
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is NULL, then -1 is returned.
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EXAMPLE
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-------
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The following example registers pid for command "ls", in context of event _tep_
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and performs various searches for pid / process name mappings:
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[source,c]
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--
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#include <event-parse.h>
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...
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int ret;
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int ls_pid = 1021;
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struct tep_handle *tep = tep_alloc();
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...
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ret = tep_register_comm(tep, "ls", ls_pid);
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if (ret != 0 && errno == EEXIST)
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ret = tep_override_comm(tep, "ls", ls_pid);
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if (ret != 0) {
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/* Failed to register pid / command mapping */
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}
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...
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if (tep_is_pid_registered(tep, ls_pid) == 0) {
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/* Command mapping for ls_pid is not registered */
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}
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...
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const char *comm = tep_data_comm_from_pid(tep, ls_pid);
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if (comm) {
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/* Found process name for ls_pid */
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}
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...
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int pid;
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struct cmdline *cmd = tep_data_pid_from_comm(tep, "ls", NULL);
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while (cmd) {
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pid = tep_cmdline_pid(tep, cmd);
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/* Found pid for process "ls" */
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cmd = tep_data_pid_from_comm(tep, "ls", cmd);
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}
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--
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FILES
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-----
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[verse]
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--
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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*-ltraceevent*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtraceevent(3)_, _trace-cmd(1)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtraceevent is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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