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>Chapter 27. Debugging Techniques</TD
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CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="KERNEL-INSTRUMENTATION">Kernel Instrumentation</H1
><P
><I
CLASS="FIRSTTERM"
>Instrument buffers</I
> can be used to
find out how many events of a given type happened in the
kernel during execution of a program.</P
><P
>You can monitor a class of several types of events, or
you can just look at individual events. </P
><P
>Examples of <I
CLASS="FIRSTTERM"
>events</I
> that can be
monitored are:
</P
><P
></P
><UL
><LI
><P
>scheduler events </P
></LI
><LI
><P
>thread operations</P
></LI
><LI
><P
>interrupts </P
></LI
><LI
><P
>mutex operations </P
></LI
><LI
><P
>binary semaphore operations </P
></LI
><LI
><P
>counting semaphore operations </P
></LI
><LI
><P
>clock ticks and interrupts </P
></LI
></UL
><P
>Examples of fine-grained scheduler event types are: </P
><P
></P
><UL
><LI
><P
>scheduler lock</P
></LI
><LI
><P
>scheduler unlock</P
></LI
><LI
><P
>rescheduling</P
></LI
><LI
><P
>time slicing </P
></LI
></UL
><P
>Information about the events is stored in an
<I
CLASS="FIRSTTERM"
>event record</I
>. The structure that
defines this record has type <SPAN
CLASS="TYPE"
>struct
Instrument_Record</SPAN
>:</P
><P
>The list of records is stored in an array called <SPAN
CLASS="TYPE"
>instrument_buffer</SPAN
>
which you can let the kernel provide or you can provide yourself
by setting the configuration option <TT
CLASS="LITERAL"
>CYGVAR_KERNEL_INSTRUMENT_EXTERNAL_BUFFER</TT
>. </P
><P
>To write a program that examines the instrumentation
buffers: </P
><P
></P
><OL
TYPE="1"
><LI
><P
>Enable instrumentation buffers in the <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> kernel configuration.
The component macro is <TT
CLASS="LITERAL"
>CYGPKG_KERNEL_INSTRUMENT</TT
>.</P
></LI
><LI
><P
>To allocate the buffers yourself, enable the configuration
option <TT
CLASS="LITERAL"
>CYGVAR_KERNEL_INSTRUMENT_EXTERNAL_BUFFER</TT
>. </P
></LI
><LI
><P
>Include the header file
<TT
CLASS="FILENAME"
>cyg/kernel/instrmnt.h</TT
>
.
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#include <cyg/kernel/instrmnt.h></PRE
></TD
></TR
></TABLE
></P
></LI
><LI
><P
>The <SPAN
CLASS="STRUCTNAME"
>Instrumentation_Record</SPAN
> structure
is not published in the kernel header file. In the future there
will be a cleaner mechanism to access it, but for now you should
paste into your code in the following lines:
</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>struct Instrument_Record
{
CYG_WORD16 type; // record type
CYG_WORD16 thread; // current thread id
CYG_WORD timestamp; // 32 bit timestamp
CYG_WORD arg1; // first arg
CYG_WORD arg2; // second arg
};</PRE
></TD
></TR
></TABLE
></LI
><LI
><P
>Enable the events you want to record using
<TT
CLASS="FUNCTION"
>cyg_instrument_enable()</TT
>
, and disable them later. Look at
<TT
CLASS="FILENAME"
>cyg/kernel/instrmnt.h</TT
>
and the examples below to see what events can be enabled. </P
></LI
><LI
><P
>Place the code you want to debug between the matching
functions
<TT
CLASS="FUNCTION"
>cyg_instrument_enable()</TT
>
and
<TT
CLASS="FUNCTION"
>cyg_instrument_disable()</TT
>
. </P
></LI
><LI
><P
>Examine the buffer. For now you need to look at the data
in there (the example program below shows how to do that), and future
versions of <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> will include a host-side tool to help you understand
the data. </P
></LI
></OL
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN2358"><P
><B
>Example 27-2. Using instrument buffers</B
></P
><P
>This program is also provided in the
<TT
CLASS="FILENAME"
>examples</TT
> directory.
</P
><TABLE
BORDER="5"
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>/* this is a program which uses <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> instrumentation buffers; it needs
to be linked with a kernel which was compiled with support for
instrumentation */
#include <stdio.h>
#include <pkgconf/kernel.h>
#include <cyg/kernel/instrmnt.h>
#include <cyg/kernel/kapi.h>
#ifndef CYGVAR_KERNEL_INSTRUMENT_EXTERNAL_BUFFER
# error You must configure eCos with CYGVAR_KERNEL_INSTRUMENT_EXTERNAL_BUFFER
#endif
struct Instrument_Record
{
CYG_WORD16 type; // record type
CYG_WORD16 thread; // current thread id
CYG_WORD timestamp; // 32 bit timestamp
CYG_WORD arg1; // first arg
CYG_WORD arg2; // second arg
};
struct Instrument_Record instrument_buffer[20];
cyg_uint32 instrument_buffer_size = 20;
int main(void)
{
int i;
cyg_instrument_enable(CYG_INSTRUMENT_CLASS_CLOCK, 0);
cyg_instrument_enable(CYG_INSTRUMENT_CLASS_THREAD, 0);
cyg_instrument_enable(CYG_INSTRUMENT_CLASS_ALARM, 0);
printf("Program to play with instrumentation buffer\n");
cyg_thread_delay(2);
cyg_instrument_disable(CYG_INSTRUMENT_CLASS_CLOCK, 0);
cyg_instrument_disable(CYG_INSTRUMENT_CLASS_THREAD, 0);
cyg_instrument_disable(CYG_INSTRUMENT_CLASS_ALARM, 0);
for (i = 0; i < instrument_buffer_size; ++i) {
printf("Record %02d: type 0x%04x, thread %d, ",
i, instrument_buffer[i].type, instrument_buffer[i].thread);
printf("time %5d, arg1 0x%08x, arg2 0x%08x\n",
instrument_buffer[i].timestamp, instrument_buffer[i].arg1,
instrument_buffer[i].arg2);
}
return 0;
}</PRE
></TD
></TR
></TABLE
></DIV
><P
>Here is how you could compile and run this program in the <TT
CLASS="FILENAME"
>examples</TT
> directory,
using (for example) the MN10300 simulator target: </P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="SCREEN"
>$ make XCC=mn10300-elf-gcc INSTALL_DIR=/tmp/ecos-work-mn10300/install instrument-test
mn10300-elf-gcc -c -o instrument-test.o -g -Wall -I/tmp/ecos-work-mn10300/install/include \
-ffunction-sections -fdata-sections instrument-test.c
mn10300-elf-gcc -nostartfiles -L/tmp/ecos-work-mn10300/install/lib -W1,--gc-sections -o \
instrument-test instrument-test.o -Ttarget.ld -nostdlib
$ mn10300-elf-run --board=stdeval1 instrument-test</PRE
></TD
></TR
></TABLE
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN2367"><P
><B
>Example 27-3. Instrument buffer output</B
></P
><P
>Here is the output of the
<B
CLASS="COMMAND"
>instrument-test</B
> program. Notice that in
little over 2 seconds, and with very little activity, and
with few event types enabled, it gathered 17 records. In
larger programs it will be necessary to select very few
event types for debugging. </P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>Program to play with instrumentation buffer
Record 00: type 0x0207, thread 2, time 6057, arg1 0x48001cd8, arg2 0x00000002
Record 01: type 0x0202, thread 2, time 6153, arg1 0x48001cd8, arg2 0x00000000
Record 02: type 0x0904, thread 2, time 6358, arg1 0x48001d24, arg2 0x00000000
Record 03: type 0x0905, thread 2, time 6424, arg1 0x00000002, arg2 0x00000000
Record 04: type 0x0906, thread 2, time 6490, arg1 0x00000000, arg2 0x00000000
Record 05: type 0x0901, thread 2, time 6608, arg1 0x48009d74, arg2 0x48001d24
Record 06: type 0x0201, thread 2, time 6804, arg1 0x48001cd8, arg2 0x480013e0
Record 07: type 0x0803, thread 1, time 94, arg1 0x00000000, arg2 0x00000000
Record 08: type 0x0801, thread 1, time 361, arg1 0x00000000, arg2 0x00000000
Record 09: type 0x0802, thread 1, time 548, arg1 0x00000001, arg2 0x00000000
Record 10: type 0x0803, thread 1, time 94, arg1 0x00000000, arg2 0x00000000
Record 11: type 0x0801, thread 1, time 361, arg1 0x00000001, arg2 0x00000000
Record 12: type 0x0903, thread 1, time 513, arg1 0x48009d74, arg2 0x48001d24
Record 13: type 0x0208, thread 1, time 588, arg1 0x00000000, arg2 0x00000000
Record 14: type 0x0203, thread 1, time 697, arg1 0x48001cd8, arg2 0x480013e0
Record 15: type 0x0802, thread 1, time 946, arg1 0x00000002, arg2 0x00000000
Record 16: type 0x0201, thread 1, time 1083, arg1 0x480013e0, arg2 0x48001cd8
Record 17: type 0x0000, thread 0, time 0, arg1 0x00000000, arg2 0x00000000
Record 18: type 0x0000, thread 0, time 0, arg1 0x00000000, arg2 0x00000000
Record 19: type 0x0000, thread 0, time 0, arg1 0x00000000, arg2 0x00000000</PRE
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