tracing: Add __cpumask to denote a trace event field that is a cpumask_t

The trace events have a __bitmask field that can be used for anything
that requires bitmasks. Although currently it is only used for CPU
masks, it could be used in the future for any type of bitmasks.

There is some user space tooling that wants to know if a field is a CPU
mask and not just some random unsigned long bitmask. Introduce
"__cpumask()" helper functions that work the same as the current
__bitmask() helpers but displays in the format file:

  field:__data_loc cpumask_t *[] mask;    offset:36;      size:4; signed:0;

Instead of:

  field:__data_loc unsigned long[] mask;  offset:32;      size:4; signed:0;

The main difference is the type. Instead of "unsigned long" it is
"cpumask_t *". Note, this type field needs to be a real type in the
__dynamic_array() logic that both __cpumask and__bitmask use, but the
comparison field requires it to be a scalar type whereas cpumask_t is a
structure (non-scalar). But everything works when making it a pointer.

Valentin added changes to remove the need of passing in "nr_bits" and the
__cpumask will always use nr_cpumask_bits as its size.

Link: https://lkml.kernel.org/r/20221014080456.1d32b989@rorschach.local.home

Requested-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 26 insertions, 8 deletions

diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index 1a92226202fc..fb4548a44153 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -200,6 +200,16 @@
  *
  *         __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits);
  *
+ *   __cpumask: This is pretty much the same as __bitmask but is specific for
+ *         CPU masks. The type displayed to the user via the format files will
+ *         be "cpumaks_t" such that user space may deal with them differently
+ *         if they choose to do so, and the bits is always set to nr_cpumask_bits.
+ *
+ *         __cpumask(target_cpu)
+ *
+ *         To assign a cpumask, use the __assign_cpumask() helper macro.
+ *
+ *         __assign_cpumask(target_cpus, cpumask_bits(bar));
  *
  * fast_assign: This is a C like function that is used to store the items
  *    into the ring buffer. A special variable called "__entry" will be the
@@ -212,8 +222,8 @@
  *    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.
+ *    Note, __dynamic_array, __string, __bitmask and __cpumask 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
@@ -226,6 +236,8 @@
  *
  *      For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus)
  *
+ *      For __cpumask(target_cpus) use __get_cpumask(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
@@ -288,6 +300,7 @@ TRACE_EVENT(foo_bar,
 		__dynamic_array(int,	list,   __length_of(lst))
 		__string(	str,	string			)
 		__bitmask(	cpus,	num_possible_cpus()	)
+		__cpumask(	cpum				)
 		__vstring(	vstr,	fmt,	va		)
 	),
 
@@ -299,9 +312,10 @@ TRACE_EVENT(foo_bar,
 		__assign_str(str, string);
 		__assign_vstr(vstr, fmt, va);
 		__assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
+		__assign_cpumask(cpum, cpumask_bits(mask));
 	),
 
-	TP_printk("foo %s %d %s %s %s %s (%s) %s", __entry->foo, __entry->bar,
+	TP_printk("foo %s %d %s %s %s %s (%s) (%s) %s", __entry->foo, __entry->bar,
 
 /*
  * Notice here the use of some helper functions. This includes:
@@ -345,7 +359,8 @@ TRACE_EVENT(foo_bar,
 		  __print_array(__get_dynamic_array(list),
 				__get_dynamic_array_len(list) / sizeof(int),
 				sizeof(int)),
-		  __get_str(str), __get_bitmask(cpus), __get_str(vstr))
+		  __get_str(str), __get_bitmask(cpus), __get_cpumask(cpus),
+		  __get_str(vstr))
 );
 
 /*
@@ -542,15 +557,16 @@ DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,
 
 TRACE_EVENT(foo_rel_loc,
 
-	TP_PROTO(const char *foo, int bar, unsigned long *mask),
+	TP_PROTO(const char *foo, int bar, unsigned long *mask, const cpumask_t *cpus),
 
-	TP_ARGS(foo, bar, mask),
+	TP_ARGS(foo, bar, mask, cpus),
 
 	TP_STRUCT__entry(
 		__rel_string(	foo,	foo	)
 		__field(	int,	bar	)
 		__rel_bitmask(	bitmask,
 			BITS_PER_BYTE * sizeof(unsigned long)	)
+		__rel_cpumask(	cpumask )
 	),
 
 	TP_fast_assign(
@@ -558,10 +574,12 @@ TRACE_EVENT(foo_rel_loc,
 		__entry->bar = bar;
 		__assign_rel_bitmask(bitmask, mask,
 			BITS_PER_BYTE * sizeof(unsigned long));
+		__assign_rel_cpumask(cpumask, cpus);
 	),
 
-	TP_printk("foo_rel_loc %s, %d, %s", __get_rel_str(foo), __entry->bar,
-		  __get_rel_bitmask(bitmask))
+	TP_printk("foo_rel_loc %s, %d, %s, %s", __get_rel_str(foo), __entry->bar,
+		  __get_rel_bitmask(bitmask),
+		  __get_rel_cpumask(cpumask))
 );
 #endif