Re: [LTP] clone tests fails

[Jiri Palecek <jpalecek@web.de>]

Serge E. Hallyn napsal(a):
> Quoting Michal Simek (michal.simek@petalogix.com):
>> Serge E. Hallyn wrote:
>>> Quoting Michal Simek (michal.simek@petalogix.com):
>>>> Hi Mike,
>>>>
>>>> I have one question about one your big patch
>>>>
>>>> http://git.kernel.org/?p=linux/kernel/git/galak/ltp.git;a=commitdiff;h=391dc18fe3271fbf2ca1864a5299f091c31e0018
>>>>
>>>> My question is why you add -1 in lib/cloner.c:65
>>>>
>>>> +       ret = clone(fn, (stack ? stack + stack_size - 1 : NULL),
>>>> +                       clone_flags, arg);
>>>>
>>>> In previous code in clone testcases was nothing like this.
>>>> What reason have you had to add it?
>>>
>>> Because the same thing was done in lots of places all over the
>>> testsuite (and done wrong).  This consolidates them all.
>>
>>
>> I don't have anything against consolidation. I just want to know why
>> there is that -1 which weren't in any clone testcases. Nothing more
>> nothing less.
>
> ooooh.  Because if we've done stack = malloc(stack_size), then
> stack+stack_size is 1 above the the top of stack.

If the value of the parameter is the stack pointer of the created thread, it 
shouldn't matter - the address should never be used (read or written).

Michal, I suspect the failures you see are somehow related to alignment (that 
your architecture doesn't like odd addresses). Is that right? Under x86, the 
address gets aligned (so some of the space is unused).

Perhaps both of these behaviors should be tested by LTP?

Regards
     Jiri Palecek

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