[LTP] [PATCH] tst_test.sh: achieve TST_RETRY_FUNC function in shell

[Petr Vorel]

Hi Li,

nice feature, thanks for adding it.
1 bashism to be fixed + minor issues bellow.


> Signed-off-by: Li Wang <liwang@redhat.com>
Tested-by: Petr Vorel <pvorel@suse.cz>

> ---
>  doc/test-writing-guidelines.txt | 20 ++++++++++++++++++++
>  testcases/lib/tst_test.sh       | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)

> diff --git a/doc/test-writing-guidelines.txt b/doc/test-writing-guidelines.txt
> index cbbfe6c..318eca6 100644
> --- a/doc/test-writing-guidelines.txt
> +++ b/doc/test-writing-guidelines.txt
> @@ -1640,6 +1640,26 @@ that can sleep for defined amount of seconds, milliseconds or microseconds.
>  tst_sleep 100ms
>  -------------------------------------------------------------------------------

> +Retry a function in limited time
> +++++++++++++++++++++++++++++++++
> +
> +Sometimes LTP test needs retrying a function for many times to get success.
> +This achievement makes that possible via keeping it retrying if the return
> +value of the function is NOT as we expected. After exceeding one second, the
> +test will break from the retries immediately.
> +
> +[source,c]
> +-------------------------------------------------------------------------------
> +# retry function in 1 second
> +TST_RETRY_FUNC(FUNC, ERET)
C docs should have been added in c2ce4df67d. Maybe you could just mention this in commit
message.

> +-------------------------------------------------------------------------------
> +
> +[source,sh]
> +-------------------------------------------------------------------------------
> +# retry function in 1 second
> +TST_RETRY_FUNC "FUNC arg1 arg2" "ERET"
Maybe EXPECTED_RET to be clearer?

> +-------------------------------------------------------------------------------
> +
>  Checking for integers
>  +++++++++++++++++++++

> +TST_RETRY_FN_EXP_BACKOFF()
> +{
> +	local tst_fun=$1
> +	local tst_exp=$2
I'd check number of params ($#) and tst_brk to warn user about improper usage.
And mention TST_RETRY_FN_EXP_BACKOFF() in docs?

> +	local tst_sec=$(expr $3 \* 1000000)
> +	local tst_delay=1
> +
> +	while true; do
> +		$tst_fun
> +		if [ "$?" == "$tst_exp" ]; then
                  ^
This is bashism, it's broken in dash. Please use single equal sign:
		if [ "$?" = "$tst_exp" ]; then


> +			break
> +		fi
> +
> +		if [ $tst_delay -lt $tst_sec ]; then
> +			tst_sleep ${tst_delay}us
> +			tst_delay=$((tst_delay*2))
> +		else
> +			tst_brk TBROK "$tst_fun failed"
> +		fi
> +	done
> +
> +	return $tst_exp
> +}
> +
> +TST_RETRY_FUNC()
> +{
> +	TST_RETRY_FN_EXP_BACKOFF "$1" "$2" 1
> +	return $2
> +}
> +
>  tst_umount()
>  {
>  	local device="$1"


Kind regards,
Petr