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156 lines
5.2 KiB
156 lines
5.2 KiB
libtraceevent(3) |
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================ |
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NAME |
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---- |
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tep_register_event_handler, tep_unregister_event_handler - Register / |
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unregisters a callback function to parse an event information. |
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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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enum *tep_reg_handler* { |
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_TEP_REGISTER_SUCCESS_, |
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_TEP_REGISTER_SUCCESS_OVERWRITE_, |
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}; |
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int *tep_register_event_handler*(struct tep_handle pass:[*]_tep_, int _id_, const char pass:[*]_sys_name_, const char pass:[*]_event_name_, tep_event_handler_func _func_, void pass:[*]_context_); |
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int *tep_unregister_event_handler*(struct tep_handle pass:[*]tep, int id, const char pass:[*]sys_name, const char pass:[*]event_name, tep_event_handler_func func, void pass:[*]_context_); |
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typedef int (*pass:[*]tep_event_handler_func*)(struct trace_seq pass:[*]s, struct tep_record pass:[*]record, struct tep_event pass:[*]event, void pass:[*]context); |
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-- |
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DESCRIPTION |
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----------- |
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The _tep_register_event_handler()_ function registers a handler function, |
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which is going to be called to parse the information for a given event. |
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The _tep_ argument is the trace event parser context. The _id_ argument is |
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the id of the event. The _sys_name_ argument is the name of the system, |
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the event belongs to. The _event_name_ argument is the name of the event. |
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If _id_ is >= 0, it is used to find the event, otherwise _sys_name_ and |
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_event_name_ are used. The _func_ is a pointer to the function, which is going |
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to be called to parse the event information. The _context_ argument is a pointer |
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to the context data, which will be passed to the _func_. If a handler function |
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for the same event is already registered, it will be overridden with the new |
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one. This mechanism allows a developer to override the parsing of a given event. |
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If for some reason the default print format is not sufficient, the developer |
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can register a function for an event to be used to parse the data instead. |
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The _tep_unregister_event_handler()_ function unregisters the handler function, |
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previously registered with _tep_register_event_handler()_. The _tep_ argument |
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is the trace event parser context. The _id_, _sys_name_, _event_name_, _func_, |
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and _context_ are the same arguments, as when the callback function _func_ was |
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registered. |
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The _tep_event_handler_func_ is the type of the custom event handler |
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function. The _s_ argument is the trace sequence, it can be used to create a |
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custom string, describing the event. A _record_ to get the event from is passed |
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as input parameter and also the _event_ - the handle to the record's event. The |
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_context_ is custom context, set when the custom event handler is registered. |
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RETURN VALUE |
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------------ |
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The _tep_register_event_handler()_ function returns _TEP_REGISTER_SUCCESS_ |
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if the new handler is registered successfully or |
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_TEP_REGISTER_SUCCESS_OVERWRITE_ if an existing handler is overwritten. |
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If there is not enough memory to complete the registration, |
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TEP_ERRNO__MEM_ALLOC_FAILED is returned. |
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The _tep_unregister_event_handler()_ function returns 0 if _func_ was removed |
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successful or, -1 if the event was not found. |
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The _tep_event_handler_func_ should return -1 in case of an error, |
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or 0 otherwise. |
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EXAMPLE |
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------- |
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[source,c] |
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-- |
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#include <event-parse.h> |
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#include <trace-seq.h> |
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... |
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struct tep_handle *tep = tep_alloc(); |
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... |
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int timer_expire_handler(struct trace_seq *s, struct tep_record *record, |
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struct tep_event *event, void *context) |
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{ |
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trace_seq_printf(s, "hrtimer="); |
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if (tep_print_num_field(s, "0x%llx", event, "timer", record, 0) == -1) |
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tep_print_num_field(s, "0x%llx", event, "hrtimer", record, 1); |
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trace_seq_printf(s, " now="); |
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tep_print_num_field(s, "%llu", event, "now", record, 1); |
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tep_print_func_field(s, " function=%s", event, "function", record, 0); |
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return 0; |
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} |
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... |
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int ret; |
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ret = tep_register_event_handler(tep, -1, "timer", "hrtimer_expire_entry", |
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timer_expire_handler, NULL); |
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if (ret < 0) { |
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char buf[32]; |
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tep_strerror(tep, ret, buf, 32) |
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printf("Failed to register handler for hrtimer_expire_entry: %s\n", buf); |
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} else { |
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switch (ret) { |
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case TEP_REGISTER_SUCCESS: |
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printf ("Registered handler for hrtimer_expire_entry\n"); |
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break; |
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case TEP_REGISTER_SUCCESS_OVERWRITE: |
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printf ("Overwrote handler for hrtimer_expire_entry\n"); |
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break; |
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} |
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} |
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... |
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ret = tep_unregister_event_handler(tep, -1, "timer", "hrtimer_expire_entry", |
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timer_expire_handler, NULL); |
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if ( ret ) |
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printf ("Failed to unregister handler for hrtimer_expire_entry\n"); |
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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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*trace-seq.h* |
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Header file to include in order to have access to trace sequences |
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related APIs. Trace sequences are used to allow a function to call |
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several other functions to create a string of data to use. |
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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* <[email protected]>, author of *libtraceevent*. |
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*Tzvetomir Stoyanov* <[email protected]>, 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 <[email protected]> |
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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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