path: root/samples/trace_events/trace-events-sample.h
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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2015-07-17 14:03:26 -0400
committerSteven Rostedt <rostedt@goodmis.org>2015-07-17 14:15:13 -0400
commitd6726c8145290bef950ae2538ea6ae1d96a1944b (patch)
treed243219746a59762fe75bbc9702325529985db19 /samples/trace_events/trace-events-sample.h
parenttracing: Have branch tracer use recursive field of task struct (diff)
tracing: Fix sample output of dynamic arrays
He Kuang noticed that the trace event samples for arrays was broken: "The output result of trace_foo_bar event in traceevent samples is wrong. This problem can be reproduced as following: (Build kernel with SAMPLE_TRACE_EVENTS=m) $ insmod trace-events-sample.ko $ echo 1 > /sys/kernel/debug/tracing/events/sample-trace/foo_bar/enable $ cat /sys/kernel/debug/tracing/trace event-sample-980 [000] .... 43.649559: foo_bar: foo hello 21 0x15 BIT1|BIT3|0x10 {0x1,0x6f6f6e53,0xff007970,0xffffffff} Snoopy ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The array length is not right, should be {0x1}. (ffffffff,ffffffff) event-sample-980 [000] .... 44.653827: foo_bar: foo hello 22 0x16 BIT2|BIT3|0x10 {0x1,0x2,0x646e6147,0x666c61,0xffffffff,0xffffffff,0x750aeffe,0x7} ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The array length is not right, should be {0x1,0x2}. Gandalf (ffffffff,ffffffff)" This was caused by an update to have __print_array()'s second parameter be the count of items in the array and not the size of the array. As there is already users of __print_array(), it can not change. But the sample code can and we can also improve on the documentation about __print_array() and __get_dynamic_array_len(). Link: http://lkml.kernel.org/r/1436839171-31527-2-git-send-email-hekuang@huawei.com Fixes: ac01ce1410fc2 ("tracing: Make ftrace_print_array_seq compute buf_len") Reported-by: He Kuang <hekuang@huawei.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'samples/trace_events/trace-events-sample.h')
1 files changed, 5 insertions, 2 deletions
diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index 8965d1bb8811..125d6402f64f 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -168,7 +168,10 @@
* 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.
+ * saved. Note, __get_dynamic_array_len() returns the total allocated
+ * length of the dynamic array; __print_array() expects the second
+ * parameter to be the number of elements. To get that, the array length
+ * needs to be divided by the element size.
* For __string(foo, bar) use __get_str(foo)
@@ -288,7 +291,7 @@ TRACE_EVENT(foo_bar,
* This prints out the array that is defined by __array in a nice format.
- __get_dynamic_array_len(list),
+ __get_dynamic_array_len(list) / sizeof(int),
__get_str(str), __get_bitmask(cpus))