[LTP] [PATCH v2] thp01: Find largest arguments size

[Richard Palethorpe]

Hello Li,

Li Wang writes:

> Cut from manual page:
>   "Traditionally, the functions execlp() and execvp() ignored all
> errors except for the ones described above and ENOMEM and E2BIG, upon
> which they returned.  They now return if any error other than the ones
> described above occurs."
>
> Let me give an example, if we just add one line in your thp01.c as:
>
> --- a/testcases/kernel/mem/thp/thp01.c
> +++ b/testcases/kernel/mem/thp/thp01.c
> @@ -65,6 +65,7 @@ static void thp_test(void)
>                         if (TEST_ERRNO != E2BIG)
>                                 tst_brk(TBROK | TTERRNO,
> "execvp(\"true\", ...)");
>
> +                       printf("debuginfo: *arg_count = %ld\n", *arg_count);
>                         *arg_count_next = *arg_count - *change;
>                         exit(0);
>                 }
>
>
>
> Compile and run thp01 as below:
>
> # ./thp01
> tst_test.c:908: INFO: Timeout per run is 0h 05m 00s
> thp01.c:76: INFO: count: 4095, change: 2047, next: 6142
> debuginfo: *arg_count = 4095
> thp01.c:76: INFO: count: 2048, change: 1023, next: 3071
> debuginfo: *arg_count = 2048
> thp01.c:76: INFO: count: 1025, change: 511, next: 1536
> thp01.c:76: INFO: count: 1536, change: 255, next: 1791
> debuginfo: *arg_count = 1536
> thp01.c:76: INFO: count: 1281, change: 127, next: 1408
> thp01.c:76: INFO: count: 1408, change: 63, next: 1471
> thp01.c:76: INFO: count: 1471, change: 31, next: 1502
> thp01.c:76: INFO: count: 1502, change: 15, next: 1517
> thp01.c:76: INFO: count: 1517, change: 7, next: 1524
> thp01.c:76: INFO: count: 1524, change: 3, next: 1527
> thp01.c:76: INFO: count: 1527, change: 1, next: 1528
> thp01.c:95: PASS: system didn't crash, pass.
>
> Summary:
> passed   1
> failed   0
> skipped  0
> warnings 0
>
>
> Do you notice that some debuginfo sentence have not been printed?
> because it will be never return if the children process run
> successfully. Though the while loop finished and *chage == 1, the
> *arg_count == 1527 is still not the largest value as we expected.
>
> I'm not sure if that is on purpose, if yes, maybe you should not say
> find largest arguments size in the subject. :)
>

I set the initial value of change incorrectly, so it wasn't finding the
highest arg count value. It should now finish on either the correct
value or the correct value plus one (which is then corrected by the
linear search afterwards).

Note that I am setting *arg_count_next before and after
execvp(). Overwriting the first value if execvp fails. So I am
deliberately using the fact it does not return on success.

>
>>
>> +       pid = SAFE_FORK();
>> +       if (!pid) {
>> +               args[*arg_count] = NULL;
>> +               do {
>> +                       TEST(execvp("true", args));
>> +                       if (TEST_ERRNO != E2BIG)
>> +                               tst_brk(TBROK | TTERRNO, "execvp(\"true\", ...)");
>> +                       tst_res(TINFO, "Binary search finished on 2BIG value: %ld",
>> +                               *arg_count);
>> +                       args[--(*arg_count)] = NULL;
>> +               } while (*arg_count > 0);
>> +               exit(0);
>> +       }
>> +
>
> here also need:   tst_reap_children();

Thanks, added.

--
Thank you,
Richard.