On Tue, Dec 01, 2020 at 10:13:29AM -0800, [email protected] wrote:
> On Tue, 1 Dec 2020, Sebastien Marie wrote:
> > I have a random segfault while using threads with custom stack.
> >
> > In short, I am doing:
> > - allocate a stack space for the thread
> > - create a thread (with custom stack using pthread_attr_setstack())
> > - join the thread
> > - free the allocated stack
> > - create a new thread, etc...
> >
> > If I remove the fact to free the allocate stack once done, it seems
> > fine (but reach ENOMEM after a while).
> >
> > I am suspecting some state corruption or stack reuse, but I can't find
> > where for now. Or am I doing bad thing and I shouldn't deallocate the
> > stack at his place ?
>
> You should not deallocate the stack. To quote POSIX, XSI 2.9.8:
>
>
> 2.9.8 Use of Application-Managed Thread Stacks
>
> An "application-managed thread stack" is a region of memory allocated
> by the application--or
> example, memory returned by the malloc() or mmap() functions--and
> designated as a stack
> through the act of passing the address and size of the stack,
> respectively, as the stackaddr and
> stacksize arguments to pthread_attr_setstack(). Application-managed
> stacks allow the application
> to precisely control the placement and size of a stack.
>
> The application grants to the implementation permanent ownership of
> and control over the
> application-managed stack when the attributes object in which the
> stack or stackaddr attribute has
> been set is used, either by presenting that attribute's object as the
> attr argument in a call to
> pthread_create() that completes successfully, or by storing a pointer
> to the attributes object in the
> sigev_notify_attributes member of a struct sigevent and passing that
> struct sigevent to a function
> accepting such argument that completes successfully. The application
> may thereafter utilize the
> memory within the stack only within the normal context of stack usage
> within or properly
> synchronized with a thread that has been scheduled by the
> implementation with stack pointer
> value(s) that are within the range of that stack. In particular, the
> region of memory cannot be
> freed, nor can it be later specified as the stack for another thread.
>
>
> Note that last sentence.
>
>
> Philip Guenther
>
The man page is lacking or even wrong in this respect. It explicitly
talks about how to do deallocation.
-Otto
