pthread_getattr_np does not work

xuelin.tian at xuelin.tian at
Tue Sep 26 11:52:52 UTC 2017

You mean, I allocate an array of some size in another thread, and set the pointer of this array as the stack address using pthread_attr_setstackaddr?

Best wishes,
xuelin.tian at
From: Joel Sherrill
Date: 2017-09-26 00:29
To: xuelin.tian at
CC: users at; Sebastian Huber
Subject: Re: Re: pthread_getattr_np does not work
I would suggest adding a test of another thread with a user provided stack
space that is properly aligned (e.g. array of double of minimum stack size
divided by sizeof(double)). This would give you known address range and
size for that thread.

For the case of RTEMS allocating the stack, the pointer returned to you
will vary based on the BSP and will essentially be random to the application.
If the application allocates it, then it knows the starting address.

You should be able to add that to the existing test without much trouble.


On Sun, Sep 24, 2017 at 9:45 PM, xuelin.tian at <xuelin.tian at> wrote:
OK, I will try to do this.

Best wishes,
xuelin.tian at
From: Joel Sherrill
Date: 2017-09-24 21:32
To: xuelin.tian
CC: rtems-users at; Sebastian Huber
Subject: Re: Re: pthread_getattr_np does not work
No. But you are welcome to submit patches so the behavior matches Linux.

On Sep 24, 2017 1:09 AM, "xuelin.tian" <xuelin.tian at> wrote:
So, is there a substitute function for this in RTEMS, without modifying the source code?
------------------ Original ------------------
From:  "Joel Sherrill"<joel at>;
Date:  Sun, Sep 24, 2017 00:15 AM
To:  "xuelin.tian"<xuelin.tian at>; 
Cc:  "Sebastian Huber"<sebastian.huber at>; "users at"<users at>; 
Subject:  Re: Re: pthread_getattr_np does not work

On Fri, Sep 22, 2017 at 9:26 PM, xuelin.tian <xuelin.tian at> wrote:
Thanks so much for your test. 

No problem. Just trying to help.
The parts of this structure I care about most are the stackaddr and stacksize (and guardsize maybe), where stackaddr always returns 0. The value of stacksize is either 8192 or 0, based on the fact that this attribute structure is retrieved from POSIX_Init or other pthreads in my system (maybe I use pthread_create in a wrong way...). 

Without looking at the code, 8192 is almost certainly the port specific default 
stack size since it is normally a value like that. A stack size request of anything
less than the recommended minimum will always get you an allocation of the
minimum. So 0 or 8192 might simply indicate whether the structure is explicitly 
initialized via pthread_attr_init() or filled in explicitly by the application with
the minimum stack size constant. 

So, from the result you post, the stackaddr is 0 too, which means this element is not supported in rtems, or there is something wrong with this function?

This means the user application didn't specify the stack area in RTEMS. Since
this method is "NP", there is no standard specifying the behavior.

This method doesn't exist on FreeBSD and appears to only exist in Linux and
RTEMS. If there is consensus that it should behave the same on Linux and
RTEMS, then there should be a ticket filed with (hopefully) patches. <hint>

It isn't a complicated method and all if should take is filling in the attribute
structure with different fields in the TCB. I think it primarily parrots back
the attribute structure passed to pthread_create().

Also writing the man page for the RTEMS POSIX manual would be appreciated.

Nothing like wandering into something that is even beyond unspecified in
POSIX to a method that is explicitly non-portable for fun. :)


------------------ Original ------------------
From:  "Joel Sherrill"<joel at>;
Date:  Fri, Sep 22, 2017 10:15 PM
To:  "xuelin.tian at"<xuelin.tian at>; 
Cc:  "Sebastian Huber"<sebastian.huber at>; "users at"<users at>; 
Subject:  Re: Re: pthread_getattr_np does not work
The test does verify the values. I don't see a specific case of creating a thread
with a non-standard stack value and verifying that value in the task but the
test creates a thread which retrieves its values and verifies many (most, all?)
of them:

Thread - pthread_getattr_np - Verify value
46        sc = pthread_getattr_np( Thread_id, &attr );
47        rtems_test_assert( sc == 0 );
52        puts( "Thread - pthread_setschedparam: Setting highest priority SCHED_FIFO" );
(gdb) p attr
$1 = {is_initialized = 1, stackaddr = 0x0, stacksize = 8192, 
  contentionscope = 0, inheritsched = 2, schedpolicy = 2, schedparam = {
    sched_priority = 3, sched_ss_low_priority = 285216961, 
    sched_ss_repl_period = {tv_sec = 0, tv_nsec = 16}, 
    sched_ss_init_budget = {tv_sec = 0, tv_nsec = 1}, sched_ss_max_repl = 0}, 
  guardsize = 0, cputime_clock_allowed = 1, detachstate = 1, 
  affinitysetsize = 0, affinityset = 0x0, affinitysetpreallocated = {
    __bits = {0}}}

Clearly the attribute structure returned is not all zero.

I am not sure what you are seeing but it doesn't match what I see in
this test on the erc32.


On Fri, Sep 22, 2017 at 4:04 AM, xuelin.tian at <xuelin.tian at> wrote:
OK, no problem, thanks anyway.

Best wishes,
xuelin.tian at
From: Sebastian Huber
Date: 2017-09-22 16:58
To: xuelin.tian at; users at
Subject: Re: pthread_getattr_np does not work
On 22/09/17 10:55, xuelin.tian at wrote:
> OK, I will try to do some fix on this function. And if Sherrill and 
> you have time, please take some time on this. Thanks a lot.
No, sorry. I have no time to fix this.
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at
PGP     : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.

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