Port sysdeps/unix/sysv/linux/i386/tst-bz21269.c to __atomic builtins

The upstream test uses <stdatomic.h>, which is not supported in the

Red Hat Enterprise Linux 7 system compiler.

The port uses __ATOMIC_SEQ_CST for consistency with the upstream test;

such as trong memory ordering is not actually required here.

Furthermore, it is necessary to change the SYS_ system call constants

to __NR_ constants.  Downstream builts the test with internal headers,

and those only have the __NR_ constants from the kernel.

The initializer of sa in xsethandler was replaced with a memset, to

avoid a warning about missing braces in an initializer (something that

later GCC versions do not warn about).

diff --git a/sysdeps/unix/sysv/linux/i386/tst-bz21269.c b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c

index 6ee3fc62be0d3312..f58395cedc6972c4 100644

--- a/sysdeps/unix/sysv/linux/i386/tst-bz21269.c

+++ b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c

@@ -26,8 +26,6 @@

    - Replicate only the test required to trigger the issue for the

      BZ#21269.  */

-#include <stdatomic.h>

-

 #include <asm/ldt.h>

 #include <linux/futex.h>

@@ -36,6 +34,7 @@

 #include <errno.h>

 #include <sys/syscall.h>

 #include <sys/mman.h>

+#include <string.h>

 #include <support/xunistd.h>

 #include <support/check.h>

@@ -44,7 +43,7 @@

 static int

 xset_thread_area (struct user_desc *u_info)

 {

-  long ret = syscall (SYS_set_thread_area, u_info);

+  long ret = syscall (__NR_set_thread_area, u_info);

   TEST_VERIFY_EXIT (ret == 0);

   return ret;

 }

@@ -52,20 +51,21 @@ xset_thread_area (struct user_desc *u_info)

 static void

 xmodify_ldt (int func, const void *ptr, unsigned long bytecount)

 {

-  TEST_VERIFY_EXIT (syscall (SYS_modify_ldt, 1, ptr, bytecount) == 0);

+  TEST_VERIFY_EXIT (syscall (__NR_modify_ldt, 1, ptr, bytecount) == 0);

 }

 static int

 futex (int *uaddr, int futex_op, int val, void *timeout, int *uaddr2,

 	int val3)

 {

-  return syscall (SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3);

+  return syscall (__NR_futex, uaddr, futex_op, val, timeout, uaddr2, val3);

 }

 static void

 xsethandler (int sig, void (*handler)(int, siginfo_t *, void *), int flags)

 {

-  struct sigaction sa = { 0 };

+  struct sigaction sa;

+  memset (&sa, 0, sizeof (sa));

   sa.sa_sigaction = handler;

   sa.sa_flags = SA_SIGINFO | flags;

   TEST_VERIFY_EXIT (sigemptyset (&sa.sa_mask) == 0);

@@ -128,7 +128,7 @@ setup_low_user_desc (void)

    1: thread armed.

    2: thread should clear LDT entry 0.

    3: thread should exit.  */

-static atomic_uint ftx;

+static unsigned int ftx;

 static void *

 threadproc (void *ctx)

@@ -136,9 +136,9 @@ threadproc (void *ctx)

   while (1)

     {

       futex ((int *) &ftx, FUTEX_WAIT, 1, NULL, NULL, 0);

-      while (atomic_load (&ftx) != 2)

+      while (__atomic_load_n (&ftx, __ATOMIC_SEQ_CST) != 2)

 	{

-	  if (atomic_load (&ftx) >= 3)

+	  if (__atomic_load_n (&ftx, __ATOMIC_SEQ_CST) >= 3)

 	    return NULL;

 	}

@@ -147,7 +147,7 @@ threadproc (void *ctx)

       xmodify_ldt (1, &desc, sizeof (desc));

       /* If ftx == 2, set it to zero,  If ftx == 100, quit.  */

-      if (atomic_fetch_add (&ftx, -2) != 2)

+      if (__atomic_fetch_add (&ftx, -2, __ATOMIC_SEQ_CST) != 2)

 	return NULL;

     }

 }

@@ -190,7 +190,7 @@ do_test (void)

 	continue;

       /* Make sure the thread is ready after the last test. */

-      while (atomic_load (&ftx) != 0)

+      while (__atomic_load_n (&ftx, __ATOMIC_SEQ_CST) != 0)

 	;

       struct user_desc desc = {

@@ -214,9 +214,9 @@ do_test (void)

       asm volatile ("mov %0, %%ss" : : "r" (0x7));

       /* Fire up thread modify_ldt call.  */

-      atomic_store (&ftx, 2);

+      __atomic_store_n (&ftx, 2, __ATOMIC_SEQ_CST);

-      while (atomic_load (&ftx) != 0)

+      while (__atomic_load_n (&ftx, __ATOMIC_SEQ_CST) != 0)

 	;

       /* On success, modify_ldt will segfault us synchronously and we will

@@ -224,7 +224,7 @@ do_test (void)

       support_record_failure ();

     }

-  atomic_store (&ftx, 100);

+  __atomic_store_n (&ftx, 100, __ATOMIC_SEQ_CST);

   futex ((int*) &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);

   xpthread_join (thread);