linux-kernel - Re: [PATCH] selftests/tracing: Fix test_multiple

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Message-Id: <20251227034406.73156-1-fushuai.wang@linux.dev>
Date: Sat, 27 Dec 2025 11:44:06 +0800
From: Fushuai Wang <fushuai.wang@...ux.dev>
To: rostedt@...dmis.org
Cc: fushuai.wang@...ux.dev,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	mathieu.desnoyers@...icios.com,
	mhiramat@...nel.org,
	shuah@...nel.org,
	wangfushuai@...du.com
Subject: Re: [PATCH] selftests/tracing: Fix test_multiple_writes stall

>> 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.
>
> Never use "This patch" in a change log. See Submitting Patches:
>
> https://docs.kernel.org/process/submitting-patches.html#describe-your-changes
>
>     Describe your changes in imperative mood, e.g. “make xyzzy do frotz”
>     instead of “[This patch] makes xyzzy do frotz” or “[I] changed xyzzy to
>     do frotz”, as if you are giving orders to the codebase to change its
>     behaviour.
>
>

Thank you for pointing this out. I will follow this guideline
in future submissions.

>> 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 <wangfushuai@...du.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");
>
> Why are you doing this in the awk script?
>>
>>  						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
>
> Could add:
>
>   if ! test_multiple_writes ; then
> 	echo $ORIG > buffer_size_kb
> 	exit_fail
>   fi
>
> instead.
> 
> -- Steve

Thank you, and this looks better.
I will send a v2 shortly.

---
Regards,
WANG