[PATCH 17/18] linux: Only use 64-bit syscall if required for internal futex

[Adhemerval Zanella]

For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit syscall
if the provided timeout fits in a 32-bit one.  The 64-bit usage should
be rare since the timeout is a relative one.

Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
(with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
---
 nptl/futex-internal.c         | 52 +++++++++++++++++++++++------------
 sysdeps/nptl/futex-internal.h | 24 ++++++++++------
 2 files changed, 50 insertions(+), 26 deletions(-)

diff --git a/nptl/futex-internal.c b/nptl/futex-internal.c
index 850bf4fd83..277e60986e 100644
--- a/nptl/futex-internal.c
+++ b/nptl/futex-internal.c
@@ -32,9 +32,6 @@ __futex_abstimed_wait_common32 (unsigned int* futex_word,
   struct timespec ts32, *pts32 = NULL;
   if (abstime != NULL)
     {
-      if (! in_time_t_range (abstime->tv_sec))
-	return -EOVERFLOW;
-
       ts32 = valid_timespec64_to_timespec (*abstime);
       pts32 = &ts32;
     }
@@ -52,12 +49,28 @@ __futex_abstimed_wait_common32 (unsigned int* futex_word,
 
 static int
 __futex_abstimed_wait_common64 (unsigned int* futex_word,
-                                unsigned int expected, clockid_t clockid,
+                                unsigned int expected, int op,
                                 const struct __timespec64* abstime,
                                 int private, bool cancel)
 {
-  unsigned int clockbit;
+  if (cancel)
+    return INTERNAL_SYSCALL_CANCEL (futex_time64, futex_word, op, expected,
+				    abstime, NULL /* Unused.  */,
+				    FUTEX_BITSET_MATCH_ANY);
+  else
+    return INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op, expected,
+				  abstime, NULL /* Ununsed.  */,
+				  FUTEX_BITSET_MATCH_ANY);
+}
+
+static int
+__futex_abstimed_wait_common (unsigned int* futex_word,
+                              unsigned int expected, clockid_t clockid,
+                              const struct __timespec64* abstime,
+                              int private, bool cancel)
+{
   int err;
+  unsigned int clockbit;
 
   /* Work around the fact that the kernel rejects negative timeout values
      despite them being valid.  */
@@ -70,16 +83,19 @@ __futex_abstimed_wait_common64 (unsigned int* futex_word,
   clockbit = (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0;
   int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private);
 
-  if (cancel)
-    err = INTERNAL_SYSCALL_CANCEL (futex_time64, futex_word, op, expected,
-                                   abstime, NULL /* Unused.  */,
-                                   FUTEX_BITSET_MATCH_ANY);
+#ifdef __ASSUME_TIME64_SYSCALLS
+  err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
+					private, cancel);
+#else
+  bool is32bit = abstime != NULL ? in_time_t_range (abstime->tv_sec) : true;
+  if (!is32bit)
+    {
+      err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
+					    private, cancel);
+      if (err == -ENOSYS)
+	err = -EOVERFLOW;
+    }
   else
-    err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op, expected,
-                                 abstime, NULL /* Ununsed.  */,
-                                 FUTEX_BITSET_MATCH_ANY);
-#ifndef __ASSUME_TIME64_SYSCALLS
-  if (err == -ENOSYS)
     err = __futex_abstimed_wait_common32 (futex_word, expected, op, abstime,
                                           private, cancel);
 #endif
@@ -109,8 +125,8 @@ __futex_abstimed_wait64 (unsigned int* futex_word, unsigned int expected,
                          clockid_t clockid,
                          const struct __timespec64* abstime, int private)
 {
-  return __futex_abstimed_wait_common64 (futex_word, expected, clockid,
-                                         abstime, private, false);
+  return __futex_abstimed_wait_common (futex_word, expected, clockid,
+                                       abstime, private, false);
 }
 libc_hidden_def (__futex_abstimed_wait64)
 
@@ -120,7 +136,7 @@ __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
                                     const struct __timespec64* abstime,
                                     int private)
 {
-  return __futex_abstimed_wait_common64 (futex_word, expected, clockid,
-                                         abstime, private, true);
+  return __futex_abstimed_wait_common (futex_word, expected, clockid,
+                                       abstime, private, true);
 }
 libc_hidden_def (__futex_abstimed_wait_cancelable64)
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index 969ab2bf4b..b54fdd44c1 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -254,15 +254,23 @@ static __always_inline int
 futex_lock_pi64 (int *futex_word, const struct __timespec64 *abstime,
                  int private)
 {
-  int err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
-                                   __lll_private_flag
-                                   (FUTEX_LOCK_PI, private), 0, abstime);
-#ifndef __ASSUME_TIME64_SYSCALLS
-  if (err == -ENOSYS)
+  int err;
+#ifdef __ASSUME_TIME64_SYSCALLS
+  err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
+			       __lll_private_flag (FUTEX_LOCK_PI, private), 0,
+			       abstime);
+#else
+  bool is32bit = abstime != NULL ? in_time_t_range (abstime->tv_sec) : true;
+  if (!is32bit)
+    {
+      err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
+				   __lll_private_flag (FUTEX_LOCK_PI, private),
+				   0, abstime);
+      if (err == -ENOSYS)
+	err = -EOVERFLOW;
+    }
+  else
     {
-      if (abstime != NULL && ! in_time_t_range (abstime->tv_sec))
-        return EOVERFLOW;
-
       struct timespec ts32;
       if (abstime != NULL)
         ts32 = valid_timespec64_to_timespec (*abstime);
-- 
2.30.2