#define _GNU_SOURCE #include <pthread.h> #include <stdio.h> int main (void) { pthread_attr_t attr; size_t size; void *stackaddr; (void) pthread_getattr_np(pthread_self(), &attr); (void) pthread_attr_getstack(&attr, &stackaddr, &size); printf ("stackaddr = 0x%x size = 0x%x\n", stackaddr, size); return 0; } The above program prints the default initial main stack size. Similar code exists in ruby thread-pthread.c. The default main stack size on hppa is 135168. It is approximately 8380416 on x86. There is some variation due to randomization. The small initial main stack on hppa causes various recursive tests in ruby to fail even though there is still lots of room for the stack to grow. The size of the stack mmap region in /proc/self/maps on hppa and x86 is identical (135168 bytes). On x86, the stack size returned is roughly rl.rlim_cur - 135168. I believe as the stack grows downward (mmap region gets larger), the x86 stack size gets smaller. I may be wrong but I don't believe the value returned on x86 is consistent with the Open Group specification. This change makes hppa behave like x86: diff --git a/nptl/pthread_getattr_np.c b/nptl/pthread_getattr_np.c index e98e2df152..43dd16d59c 100644 --- a/nptl/pthread_getattr_np.c +++ b/nptl/pthread_getattr_np.c @@ -145,9 +145,9 @@ __pthread_getattr_np (pthread_t thread_id, pthread_attr_t *attr) > (size_t) iattr->stackaddr - last_to) iattr->stacksize = (size_t) iattr->stackaddr - last_to; #else - /* The limit might be too high. */ + /* The limit might be too low. */ if ((size_t) iattr->stacksize - > to - (size_t) iattr->stackaddr) + < to - (size_t) iattr->stackaddr) iattr->stacksize = to - (size_t) iattr->stackaddr; #endif /* We succeed and no need to look further. */ But I think the x86 code is wrong. Shouldn't pthread_attr_getstacksize and pthread_attr_getstack return the actual stack size at the time of their call? They currently return the unallocated residual. getrlimit can be be used to get the maximum size of the process stack. Open Group spec says: The stacksize attribute shall define the minimum stack size (in bytes) allocated for the created threads stack.
commit 8e86549d1417a4618ab98d10aaba427350b321c6 (HEAD -> master, origin/master, origin/HEAD) Author: John David Anglin <danglin@gcc.gnu.org> Date: Wed Jan 29 16:51:16 2025 -0500 nptl: Correct stack size attribute when stack grows up [BZ #32574] Set stack size attribute to the size of the mmap'd region only when the size of the remaining stack space is less than the size of the mmap'd region. This was reversed. As a result, the initial stack size was only 135168 bytes. On architectures where the stack grows down, the initial stack size is approximately 8384512 bytes with the default rlimit settings. The small main stack size on hppa broke applications like ruby that check for stack overflows. Signed-off-by: John David Anglin <dave.anglin@bell.net> Fixed in 2.42.