From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 21 Nov 2008 16:23:08 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-core] [PATCH] Catch multiple xnshadow_map attempts
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Philippe Gerum wrote:
> Philippe Gerum wrote:
>> Jan Kiszka wrote:
>>> Philippe Gerum wrote:
>>>> Jan Kiszka wrote:
>>>>> My customer managed to find another hidden door to Xenomai's hell:
>>>>> Trying to create a Xenomai POSIX thread from within a native thread. A
>>>>> think the other way around would "work" as well. The precise scenario
>>>>> was native thread -> dlopen(libs that's linked against libpthread_rt) ->
>>>>> __init_posix_interface -> __wrap_pthread_setschedparam -> oops. That
>>>>> scenario revealed two more issues in fact.
>>>>>
>>>>> Here is a patch to remove this hell gate by catching xnshadow_map
>>>>> invocations from withing already mapped shadow thread.
>>>>>
>>>> Any reason why the XNMAPPED predicate did not work in your case?
>>> Sorry, which one? Keep in mind that the thread thrown at the second
>>> xnshadow_map is a virgin one, just allocated from scratch.
>>>
>> Ok, got it, it's the converse case, so let's deal for that:
>>
>> --- ksrc/nucleus/shadow.c	(revision 4411)
>> +++ ksrc/nucleus/shadow.c	(working copy)
>> @@ -1331,7 +1331,7 @@
>>   * case, the real-time mapping operation has failed globally, and no
>>   * Xenomai resource remains attached to it.
>>   *
>> - * - -EINVAL is returned if the thread control block does not bear the
>> + * - -EBUSY is returned if the thread control block does not bear the
>>   * XNSHADOW bit, or if the thread has already been mapped.
>>   *
>>   * Environments:
>> @@ -1354,8 +1354,8 @@
>>  	if (!xnthread_test_state(thread, XNSHADOW))
>>  		return -EINVAL;
>>
>> -	if (xnthread_test_state(thread, XNMAPPED))
>> -		return -EINVAL;
>> +	if (xnshadow_thread(current) || xnthread_test_state(thread, XNMAPPED))
>> +		return -EBUSY;
>>
>>  	if (!access_wok(u_mode, sizeof(*u_mode)))
>>  		return -EFAULT;
>>
> 
> --- ksrc/nucleus/shadow.c	(revision 4411)
> +++ ksrc/nucleus/shadow.c	(working copy)
> @@ -1332,8 +1332,10 @@
>   * Xenomai resource remains attached to it.
>   *
>   * - -EINVAL is returned if the thread control block does not bear the
> - * XNSHADOW bit, or if the thread has already been mapped.
> + * XNSHADOW bit.
>   *
> + * - -EBUSY is returned if the thread has already been mapped.
> + *
>   * Environments:

The code now returns -EBUSY if someone passes down an already touched
xnthread object - for me a clear case of EINVAL (the object should be a
virgin one). EBUSY should be dedicated to the case that the current
_Linux_task_ is already mapped (to some other xnthread object). I think
my patch is clearer in this respect.

Jan

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