[PATCH] selftests/tracing: Fix test_multiple_writes stall

[Fushuai Wang]

When /sys/kernel/tracing/buffer_size_kb is less than 12KB,
the test_multiple_writes test will stall and wait for more
input due to insufficient buffer space.

This patch check current buffer_size_kb value before the test.
If it is less than 12KB, it temporarily increase the buffer to
12KB, and restore the original value after the tests are completed.

Fixes: 37f46601383a ("selftests/tracing: Add basic test for trace_marker_raw 
file")
Signed-off-by: Fushuai Wang <wangfush...@baidu.com>
---
 .../ftrace/test.d/00basic/trace_marker_raw.tc    | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc 
b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
index 7daf7292209e..216f87d89c3f 100644
--- a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
+++ b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc
@@ -58,7 +58,7 @@ test_multiple_writes() {
        echo stop > trace_marker
 
        # Check to make sure the number of entries is the id (rounded up by 4)
-       awk '/.*: # [0-9a-f]* / {
+       awk -v ORIG="${ORIG}" '/.*: # [0-9a-f]* / {
                        print;
                        cnt = -1;
                        for (i = 0; i < NF; i++) {
@@ -70,6 +70,7 @@ test_multiple_writes() {
                                        # The number of items is always rounded 
up by 4
                                        cnt2 = int((cnt + 3) / 4) * 4;
                                        if (cnt2 != num) {
+                                               system("echo \""ORIG"\" > 
buffer_size_kb");
                                                exit 1;
                                        }
                                        break;
@@ -89,6 +90,7 @@ test_buffer() {
        # The id must be four bytes, test that 3 bytes fails a write
        if echo -n abc > ./trace_marker_raw ; then
                echo "Too small of write expected to fail but did not"
+               echo $ORIG > buffer_size_kb
                exit_fail
        fi
 
@@ -99,9 +101,21 @@ test_buffer() {
 
        if write_buffer 0xdeadbeef $size ; then
                echo "Too big of write expected to fail but did not"
+               echo $ORIG > buffer_size_kb
                exit_fail
        fi
 }
 
+ORIG=`cat buffer_size_kb`
+
+# test_multiple_writes test needs at least 12KB buffer
+NEW_SIZE=12
+
+if [ ${ORIG} -lt ${NEW_SIZE} ]; then
+       echo ${NEW_SIZE} > buffer_size_kb
+fi
+
 test_buffer
 test_multiple_writes
+
+echo $ORIG > buffer_size_kb
-- 
2.36.1