diff options
Diffstat (limited to 'samples/trace_events/trace-events-sample.h')
| -rw-r--r-- | samples/trace_events/trace-events-sample.h | 145 |
1 files changed, 132 insertions, 13 deletions
diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h index 476429281389..dd65f7b8c0d9 100644 --- a/samples/trace_events/trace-events-sample.h +++ b/samples/trace_events/trace-events-sample.h @@ -1,6 +1,6 @@ /* * If TRACE_SYSTEM is defined, that will be the directory created - * in the ftrace directory under /sys/kernel/debug/tracing/events/<system> + * in the ftrace directory under /sys/kernel/tracing/events/<system> * * The define_trace.h below will also look for a file name of * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. @@ -54,44 +54,163 @@ * Here it is simply "foo, bar". * * struct: This defines the way the data will be stored in the ring buffer. - * There are currently two types of elements. __field and __array. - * a __field is broken up into (type, name). Where type can be any - * primitive type (integer, long or pointer). __field_struct() can - * be any static complex data value (struct, union, but not an array). - * For an array. there are three fields. (type, name, size). The - * type of elements in the array, the name of the field and the size - * of the array. + * The items declared here become part of a special structure + * called "__entry", which can be used in the fast_assign part of the + * TRACE_EVENT macro. + * + * Here are the currently defined types you can use: + * + * __field : Is broken up into type and name. Where type can be any + * primitive type (integer, long or pointer). + * + * __field(int, foo) + * + * __entry->foo = 5; + * + * __field_struct : This can be any static complex data type (struct, union + * but not an array). Be careful using complex types, as each + * event is limited in size, and copying large amounts of data + * into the ring buffer can slow things down. + * + * __field_struct(struct bar, foo) + * + * __entry->bar.x = y; + + * __array: There are three fields (type, name, size). The type is the + * type of elements in teh array, the name is the name of the array. + * size is the number of items in the array (not the total size). + * + * __array( char, foo, 10) is the same as saying: char foo[10]; + * + * Assigning arrays can be done like any array: + * + * __entry->foo[0] = 'a'; + * + * memcpy(__entry->foo, bar, 10); + * + * __dynamic_array: This is similar to array, but can vary is size from + * instance to instance of the tracepoint being called. + * Like __array, this too has three elements (type, name, size); + * type is the type of the element, name is the name of the array. + * The size is different than __array. It is not a static number, + * but the algorithm to figure out the length of the array for the + * specific instance of tracepoint. Again, size is the numebr of + * items in the array, not the total length in bytes. + * + * __dynamic_array( int, foo, bar) is similar to: int foo[bar]; + * + * Note, unlike arrays, you must use the __get_dynamic_array() macro + * to access the array. + * + * memcpy(__get_dynamic_array(foo), bar, 10); + * + * Notice, that "__entry" is not needed here. + * + * __string: This is a special kind of __dynamic_array. It expects to + * have a nul terminated character array passed to it (it allows + * for NULL too, which would be converted into "(null)"). __string + * takes two paramenter (name, src), where name is the name of + * the string saved, and src is the string to copy into the + * ring buffer. + * + * __string(foo, bar) is similar to: strcpy(foo, bar) + * + * To assign a string, use the helper macro __assign_str(). + * + * __assign_str(foo, bar); + * + * In most cases, the __assign_str() macro will take the same + * parameters as the __string() macro had to declare the string. + * + * __bitmask: This is another kind of __dynamic_array, but it expects + * an array of longs, and the number of bits to parse. It takes + * two parameters (name, nr_bits), where name is the name of the + * bitmask to save, and the nr_bits is the number of bits to record. + * + * __bitmask(target_cpu, nr_cpumask_bits) + * + * To assign a bitmask, use the __assign_bitmask() helper macro. + * + * __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits); * - * __array( char, foo, 10) is the same as saying char foo[10]. * * fast_assign: This is a C like function that is used to store the items - * into the ring buffer. + * into the ring buffer. A special variable called "__entry" will be the + * structure that points into the ring buffer and has the same fields as + * described by the struct part of TRACE_EVENT above. * * printk: This is a way to print out the data in pretty print. This is * useful if the system crashes and you are logging via a serial line, * the data can be printed to the console using this "printk" method. + * This is also used to print out the data from the trace files. + * Again, the __entry macro is used to access the data from the ring buffer. + * + * Note, __dynamic_array, __string, and __bitmask require special helpers + * to access the data. + * + * For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo) + * Use __get_dynamic_array_len(foo) to get the length of the array + * saved. + * + * For __string(foo, bar) use __get_str(foo) + * + * For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus) + * * * Note, that for both the assign and the printk, __entry is the handler * to the data structure in the ring buffer, and is defined by the * TP_STRUCT__entry. */ + +/* + * It is OK to have helper functions in the file, but they need to be protected + * from being defined more than once. Remember, this file gets included more + * than once. + */ +#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS +#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS +static inline int __length_of(const int *list) +{ + int i; + + if (!list) + return 0; + + for (i = 0; list[i]; i++) + ; + return i; +} +#endif + TRACE_EVENT(foo_bar, - TP_PROTO(char *foo, int bar), + TP_PROTO(const char *foo, int bar, const int *lst, + const char *string, const struct cpumask *mask), - TP_ARGS(foo, bar), + TP_ARGS(foo, bar, lst, string, mask), TP_STRUCT__entry( __array( char, foo, 10 ) __field( int, bar ) + __dynamic_array(int, list, __length_of(lst)) + __string( str, string ) + __bitmask( cpus, num_possible_cpus() ) ), TP_fast_assign( strlcpy(__entry->foo, foo, 10); __entry->bar = bar; + memcpy(__get_dynamic_array(list), lst, + __length_of(lst) * sizeof(int)); + __assign_str(str, string); + __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus()); ), - TP_printk("foo %s %d", __entry->foo, __entry->bar) + TP_printk("foo %s %d %s %s (%s)", __entry->foo, __entry->bar, + __print_array(__get_dynamic_array(list), + __get_dynamic_array_len(list), + sizeof(int)), + __get_str(str), __get_bitmask(cpus)) ); #endif |