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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2015-07-17 14:03:26 -0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2015-07-17 14:15:13 -0400 |
| commit | d6726c8145290bef950ae2538ea6ae1d96a1944b (patch) | |
| tree | d243219746a59762fe75bbc9702325529985db19 | |
| parent | 6224beb12e190ff11f3c7d4bf50cb2922878f600 (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>
| -rw-r--r-- | samples/trace_events/trace-events-sample.h | 7 |
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. */ __print_array(__get_dynamic_array(list), - __get_dynamic_array_len(list), + __get_dynamic_array_len(list) / sizeof(int), sizeof(int)), __get_str(str), __get_bitmask(cpus)) ); |