pthread_attr_setstackaddr(3) - NetBSD Manual Pages

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PTHREAD_ATTR_GETSTAC... NetBSD Library Functions ManualPTHREAD_ATTR_GETSTAC...


NAME

     pthread_attr_getstack, pthread_attr_setstack, pthread_attr_getstacksize,
     pthread_attr_setstacksize, pthread_attr_getstackaddr,
     pthread_attr_setstackaddr -- get and set thread stack attributes


LIBRARY

     POSIX Threads Library (libpthread, -lpthread)


SYNOPSIS

     #include <pthread.h>

     int
     pthread_attr_getstack(const pthread_attr_t * restrict attr,
         void ** restrict stackaddr, size_t * restrict stacksize);

     int
     pthread_attr_setstack(pthread_attr_t * restrict attr, void *stackaddr,
         size_t stacksize);

     int
     pthread_attr_getstacksize(const pthread_attr_t * restrict attr,
         size_t * restrict stacksize);

     int
     pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize);

     int
     pthread_attr_getstackaddr(const pthread_attr_t * restrict attr,
         void ** restrict stackaddr);

     int
     pthread_attr_setstackaddr(pthread_attr_t *attr, void *stackaddr);


DESCRIPTION

     The pthread_attr_getstack() and pthread_attr_setstack() functions get and
     set, respectively, the thread stack attributes stackaddr and stacksize in
     the attr object.  The remaining four functions behave similarly, but
     instead of getting or setting both stackaddr and stacksize, these get and
     set the values individually.

     The stacksize parameter is defined to be the minimum stack size (in
     bytes) allocated for the thread's stack during the creation of the
     thread.  The stackaddr attribute specifies the location of storage to be
     used for the thread's stack.  All pages within the stack described by
     stackaddr and stacksize should be both readable and writable by the
     thread.

     The behavior is undefined in all functions if the attr parameter does not
     refer to an attribute object initialized by using pthread_attr_init(3)
     prior to the call.  In addition, undefined behavior may follow if the
     pthread_attr_getstack() function is called before the stackaddr attribute
     has been set.

   Rationale
     The rationale behind these functions is to address cases where an appli-
     cation may be used in an environment where the stack of a thread must be
     placed to some particular region of memory.  For the majority of applica-
     tions, this is seldom necessary, and the use of these functions should be
     generally avoided.  At least few potential caveats can be mentioned.

       ·   There is a certain degree of ambiguity in the POSIX standard with
           respect to thread stack.

       ·   The exact behavior of the functions may vary both across machines
           and operating systems.  In particular, the address specified by
           stackaddr should be suitably aligned.  The system page size, as
           specified by sysconf(3), and the use of posix_memalign(3) may guar-
           antee some degree of portability.  Also mmap(2) provides means for
           alignment.

       ·   If the application modifies the stack address, it claims also the
           responsibility of allocating the stack area and guarding it against
           possible stack overflow.  No default guard area will be allocated
           (see pthread_attr_getguardsize(3)).  It may be necessary to manu-
           ally use mprotect(2) in order to define a guard area at the end of
           the allocated stack.

       ·   Moreover, if attr is used to create multiple threads, the stack
           address must be changed by the application between successive calls
           to pthread_create(3).


RETURN VALUES

     If successful, these functions return 0.  Otherwise, an error number is
     returned to indicate the error.


ERRORS

     No errors are defined for the three functions that obtain the stack val-
     ues.  The three functions that set the stack values may fail if:

     [ENOMEM]           There was insufficient memory to complete the opera-
                        tion.

     The pthread_attr_setstacksize() function may additionally fail if:

     [EINVAL]           The specified stacksize is less than PTHREAD_STACK_MIN
                        or exceeds some system-imposed limit.


SEE ALSO

     pthread_attr(3), pthread_attr_setguardsize(3)


STANDARDS

     All described functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').
     Note that pthread_attr_getstackaddr() and pthread_attr_setstackaddr()
     were however removed from the specification in the IEEE Std 1003.1-2008
     (``POSIX.1'') revision.


BUGS

     Older versions of NetBSD, prior to 10.0, 9.4, and 8.3, incorrectly adjust
     the stack address by the guard size in threads configured with
     pthread_attr_setstack(), instead of ignoring the guard size in that case
     as POSIX prescribes (see PR lib/57721:
           https://gnats.NetBSD.org/57721).

     Even if you didn't set a nonzero guard size with
     pthread_attr_setguardsize(3), the system will choose a nonzero default
     guard size.

     To work around this in applications that run on older and newer versions
     of NetBSD, as well as on other operating systems, you can safely set the
     guard size to zero:
           pthread_attr_setguardsize(&attr, 0);

NetBSD 10.1                      July 9, 2010                      NetBSD 10.1