[glibc] linux: Add ppoll time64 optimization

[glibc] linux: Add ppoll time64 optimization

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=60a2e28b34b41e1a4e50feec7b38e068c9e33eec

commit 60a2e28b34b41e1a4e50feec7b38e068c9e33eec
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Fri Jul 10 13:50:56 2020 -0300

    linux: Add ppoll time64 optimization
    
    It avoid continuing issue the __NR_ppoll_time64 syscall once the kernel
    advertise it does not support it.
    
    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/ppoll.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/ppoll.c b/sysdeps/unix/sysv/linux/ppoll.c
index dd2167fc55..e68a153427 100644
--- a/sysdeps/unix/sysv/linux/ppoll.c
+++ b/sysdeps/unix/sysv/linux/ppoll.c
@@ -22,6 +22,7 @@
 #include <sys/poll.h>
 #include <sysdep-cancel.h>
 #include <kernel-features.h>
+#include <time64-support.h>
 
 
 int
@@ -37,16 +38,23 @@ __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
       timeout = &tval;
     }
 
+  int ret;
+
+  if (supports_time64 ())
+    {
 #ifndef __NR_ppoll_time64
 # define __NR_ppoll_time64 __NR_ppoll
 #endif
-  int ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
-                            __NSIG_BYTES);
+      ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
+			    __NSIG_BYTES);
 
-#ifndef __ASSUME_TIME64_SYSCALLS
-  if (ret >= 0 || errno != ENOSYS)
-    return ret;
+      if (ret == 0 || errno != ENOSYS)
+	return ret;
 
+      mark_time64_unsupported ();
+    }
+
+#ifndef __ASSUME_TIME64_SYSCALLS
   struct timespec ts32;
   if (timeout)
     {