[glibc] linux: Simplify clock_getres

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ecdcafa571ba68e081e9cfcdda4ea8c1a9dbdf0d

commit ecdcafa571ba68e081e9cfcdda4ea8c1a9dbdf0d
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Jul 9 17:46:34 2020 -0300

    linux: Simplify clock_getres
    
    With arch-syscall.h it can now assumes the existance of either
    __NR_clock_getres or __NR_clock_getres_time64.  The 32-bit time_t
    support is now only build for !__ASSUME_TIME64_SYSCALLS.
    
    It also uses the time64-support functions to simplify it further.
    
    Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
    kernel).
    
    Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Diff:
---
 sysdeps/unix/sysv/linux/clock_getres.c | 38 ++++++++++++++--------------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/clock_getres.c b/sysdeps/unix/sysv/linux/clock_getres.c
index 5f6955ab10..6be73c94de 100644
--- a/sysdeps/unix/sysv/linux/clock_getres.c
+++ b/sysdeps/unix/sysv/linux/clock_getres.c
@@ -21,6 +21,7 @@
 #include <time.h>
 
 #include <sysdep-vdso.h>
+#include <time64-support.h>
 #include <shlib-compat.h>
 #include <kernel-features.h>
 
@@ -28,36 +29,26 @@
 int
 __clock_getres64 (clockid_t clock_id, struct __timespec64 *res)
 {
-#ifdef __ASSUME_TIME64_SYSCALLS
-  /* 64 bit ABIs or Newer 32-bit ABIs that only support 64-bit time_t.  */
-# ifndef __NR_clock_getres_time64
-#  define __NR_clock_getres_time64 __NR_clock_getres
-# endif
-# ifdef HAVE_CLOCK_GETRES64_VSYSCALL
-  return INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
-# else
-  return INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
-# endif
-#else
   int r;
-  /* Old 32-bit ABI with possible 64-bit time_t support.  */
-# ifdef __NR_clock_getres_time64
-  /* Avoid issue a __NR_clock_getres_time64 syscall on kernels that do not
-     support 64-bit time_t.  */
-  static int time64_support = 1;
-  if (atomic_load_relaxed (&time64_support) != 0)
+
+#ifndef __NR_clock_getres_time64
+# define __NR_clock_getres_time64 __NR_clock_getres
+#endif
+  if (supports_time64 ())
     {
-#  ifdef HAVE_CLOCK_GETRES64_VSYSCALL
+#ifdef HAVE_CLOCK_GETRES64_VSYSCALL
       r = INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
-#  else
+#else
       r = INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
-#  endif
+#endif
+
       if (r == 0 || errno != ENOSYS)
 	return r;
 
-      atomic_store_relaxed (&time64_support, 0);
+      mark_time64_unsupported ();
     }
-# endif
+
+#ifndef __ASSUME_TIME64_SYSCALLS
   /* Fallback code that uses 32-bit support.  */
   struct timespec ts32;
 # ifdef HAVE_CLOCK_GETRES_VSYSCALL
@@ -67,8 +58,9 @@ __clock_getres64 (clockid_t clock_id, struct __timespec64 *res)
 # endif
   if (r == 0)
     *res = valid_timespec_to_timespec64 (ts32);
-  return r;
 #endif
+
+  return r;
 }
 
 #if __TIMESIZE != 64