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Re: [gomp] Reuse futex barrier implementation for RTEMS


On 17/07/15 08:40, Sebastian Huber wrote:
Hello,

the libgomp configuration for RTEMS uses currently the POSIX implementation. Unfortunately the performance is unacceptable bad, so I work currently on a specialized RTEMS configuration. I would like to reuse the code of the Linux futex barrier. On RTEMS there is no kernel/user space separation. In order to make the futex management simpler, I would like to optionally embed a futex object in the barrier. Would a change like this be acceptable?

Attached is a more complete example.

--
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber@embedded-brains.de
PGP     : Public key available on request.

Diese Nachricht ist keine geschÃftliche Mitteilung im Sinne des EHUG.

>From 0410937e6f07dd1923dbcf20a0b2cda5953cd1cc Mon Sep 17 00:00:00 2001
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Wed, 1 Jul 2015 22:14:38 +0200
Subject: [PATCH] [gomp] Add RTEMS configuration

libgomp/ChangeLog
2015-07-18  Sebastian Huber  <sebastian.huber@embedded-brains.de>

	* config/rtems/bar.c: New.
	* config/rtems/bar.h: Likewise.
	* config/rtems/mutex.c: Likewise.
	* config/rtems/mutex.h: Likewise.
	* config/rtems/sem.c: Likewise.
	* config/rtems/sem.h: Likewise.
	* config/linux/bar.c (gomp_barrier_wait): Use
	barrier_futex_wake() instead of futex_wake().  Use
	barrier_futex_wait() instead of futex_wait().  Use
	barrier_do_wait() instead of do_wait().
	(gomp_team_barrier_wake): Likewise.
	(gomp_team_barrier_wait_end): Likewise.
	(gomp_team_barrier_wait_end): Likewise.
	(gomp_team_barrier_wait_cancel_end): Likewise.
	(gomp_team_barrier_cancel): Likewise.
	* config/linux/bar.h (gomp_barrier_t): Add optional futex
	member.
	* config/linux/wait.h (barrier_futex_wake): New.
	(barrier_futex_wait): Likewise.
	(barrier_do_wait): Likewise.
	* configure.ac (*-*-rtems*): Check that Newlib provides a proper
	<sys/lock.h> header file.
	* configure.tgt (*-*-rtems*): Enable RTEMS configuration if
	supported by Newlib.
	* configure: Regenerate.
---
 libgomp/config/linux/bar.c   | 22 ++++++++-------
 libgomp/config/linux/bar.h   |  3 ++
 libgomp/config/linux/wait.h  |  6 ++++
 libgomp/config/rtems/bar.c   | 65 ++++++++++++++++++++++++++++++++++++++++++++
 libgomp/config/rtems/bar.h   | 39 ++++++++++++++++++++++++++
 libgomp/config/rtems/mutex.c |  1 +
 libgomp/config/rtems/mutex.h | 57 ++++++++++++++++++++++++++++++++++++++
 libgomp/config/rtems/sem.c   |  1 +
 libgomp/config/rtems/sem.h   | 55 +++++++++++++++++++++++++++++++++++++
 libgomp/configure            | 17 ++++++++++++
 libgomp/configure.ac         |  7 +++++
 libgomp/configure.tgt        |  7 +++++
 12 files changed, 270 insertions(+), 10 deletions(-)
 create mode 100644 libgomp/config/rtems/bar.c
 create mode 100644 libgomp/config/rtems/bar.h
 create mode 100644 libgomp/config/rtems/mutex.c
 create mode 100644 libgomp/config/rtems/mutex.h
 create mode 100644 libgomp/config/rtems/sem.c
 create mode 100644 libgomp/config/rtems/sem.h

diff --git a/libgomp/config/linux/bar.c b/libgomp/config/linux/bar.c
index 51fbd99..920b85e 100644
--- a/libgomp/config/linux/bar.c
+++ b/libgomp/config/linux/bar.c
@@ -40,12 +40,12 @@ gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
       bar->awaited = bar->total;
       __atomic_store_n (&bar->generation, bar->generation + BAR_INCR,
 			MEMMODEL_RELEASE);
-      futex_wake ((int *) &bar->generation, INT_MAX);
+      barrier_futex_wake ((int *) &bar->generation, INT_MAX, &bar->futex);
     }
   else
     {
       do
-	do_wait ((int *) &bar->generation, state);
+	barrier_do_wait ((int *) &bar->generation, state, &bar->futex);
       while (__atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) == state);
     }
 }
@@ -74,7 +74,8 @@ gomp_barrier_wait_last (gomp_barrier_t *bar)
 void
 gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
 {
-  futex_wake ((int *) &bar->generation, count == 0 ? INT_MAX : count);
+  barrier_futex_wake ((int *) &bar->generation, count == 0 ? INT_MAX : count,
+		 &bar->futex);
 }
 
 void
@@ -100,7 +101,7 @@ gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
 	  state &= ~BAR_CANCELLED;
 	  state += BAR_INCR - BAR_WAS_LAST;
 	  __atomic_store_n (&bar->generation, state, MEMMODEL_RELEASE);
-	  futex_wake ((int *) &bar->generation, INT_MAX);
+	  barrier_futex_wake ((int *) &bar->generation, INT_MAX, &bar->futex);
 	  return;
 	}
     }
@@ -109,7 +110,7 @@ gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
   state &= ~BAR_CANCELLED;
   do
     {
-      do_wait ((int *) &bar->generation, generation);
+      barrier_do_wait ((int *) &bar->generation, generation, &bar->futex);
       gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
       if (__builtin_expect (gen & BAR_TASK_PENDING, 0))
 	{
@@ -163,7 +164,7 @@ gomp_team_barrier_wait_cancel_end (gomp_barrier_t *bar,
 	{
 	  state += BAR_INCR - BAR_WAS_LAST;
 	  __atomic_store_n (&bar->generation, state, MEMMODEL_RELEASE);
-	  futex_wake ((int *) &bar->generation, INT_MAX);
+	  barrier_futex_wake ((int *) &bar->generation, INT_MAX, &bar->futex);
 	  return false;
 	}
     }
@@ -174,7 +175,7 @@ gomp_team_barrier_wait_cancel_end (gomp_barrier_t *bar,
   generation = state;
   do
     {
-      do_wait ((int *) &bar->generation, generation);
+      barrier_do_wait ((int *) &bar->generation, generation, &bar->futex);
       gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
       if (__builtin_expect (gen & BAR_CANCELLED, 0))
 	return true;
@@ -199,13 +200,14 @@ gomp_team_barrier_wait_cancel (gomp_barrier_t *bar)
 void
 gomp_team_barrier_cancel (struct gomp_team *team)
 {
+  gomp_barrier_t *bar = &team->barrier;
   gomp_mutex_lock (&team->task_lock);
-  if (team->barrier.generation & BAR_CANCELLED)
+  if (bar->generation & BAR_CANCELLED)
     {
       gomp_mutex_unlock (&team->task_lock);
       return;
     }
-  team->barrier.generation |= BAR_CANCELLED;
+  bar->generation |= BAR_CANCELLED;
   gomp_mutex_unlock (&team->task_lock);
-  futex_wake ((int *) &team->barrier.generation, INT_MAX);
+  barrier_futex_wake ((int *) &bar->generation, INT_MAX, &bar->futex);
 }
diff --git a/libgomp/config/linux/bar.h b/libgomp/config/linux/bar.h
index 3236436..b47b9f6 100644
--- a/libgomp/config/linux/bar.h
+++ b/libgomp/config/linux/bar.h
@@ -40,6 +40,9 @@ typedef struct
   unsigned generation;
   unsigned awaited __attribute__((aligned (64)));
   unsigned awaited_final;
+#ifdef HAVE_BARRIER_FUTEX
+  gomp_barrier_futex_t futex;
+#endif
 } gomp_barrier_t;
 
 typedef unsigned int gomp_barrier_state_t;
diff --git a/libgomp/config/linux/wait.h b/libgomp/config/linux/wait.h
index 7f57454..b244494 100644
--- a/libgomp/config/linux/wait.h
+++ b/libgomp/config/linux/wait.h
@@ -65,6 +65,12 @@ static inline void do_wait (int *addr, int val)
     futex_wait (addr, val);
 }
 
+#define barrier_futex_wait(addr, val, futex) futex_wait (addr, val)
+
+#define barrier_futex_wake(addr, count, futex) futex_wake (addr, count)
+
+#define barrier_do_wait(addr, val, futex) do_wait (addr, val)
+
 #ifdef HAVE_ATTRIBUTE_VISIBILITY
 # pragma GCC visibility pop
 #endif
diff --git a/libgomp/config/rtems/bar.c b/libgomp/config/rtems/bar.c
new file mode 100644
index 0000000..a152f0a
--- /dev/null
+++ b/libgomp/config/rtems/bar.c
@@ -0,0 +1,65 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+   Contributed by Sebastian Huber <sebastian.huber@embedded-brains.de>.
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This is the RTEMS implementation of a barrier synchronization
+   mechanism for libgomp.  This type is private to the library.  */
+
+#include <libgomp.h>
+#include <bar.h>
+
+static void
+barrier_futex_wait (int *addr, int val, gomp_barrier_futex_t *futex)
+{
+  _Futex_Wait (futex, addr, val);
+}
+
+static void
+barrier_futex_wake (int *addr, int count, gomp_barrier_futex_t *futex)
+{
+  _Futex_Wake (futex, count);
+}
+
+static int
+do_spin (int *addr, int val)
+{
+  unsigned long long i, count = gomp_spin_count_var;
+
+  if (__builtin_expect (gomp_managed_threads > gomp_available_cpus, 0))
+    count = gomp_throttled_spin_count_var;
+  for (i = 0; i < count; i++)
+    if (__builtin_expect (__atomic_load_n (addr, MEMMODEL_RELAXED) != val, 0))
+      return 0;
+  return 1;
+}
+
+static void
+barrier_do_wait (int *addr, int val, gomp_barrier_futex_t *futex)
+{
+  if (do_spin (addr, val))
+    barrier_futex_wait (addr, val, futex);
+}
+
+#define GOMP_WAIT_H 1
+
+#include "../linux/bar.c"
diff --git a/libgomp/config/rtems/bar.h b/libgomp/config/rtems/bar.h
new file mode 100644
index 0000000..a9acdea
--- /dev/null
+++ b/libgomp/config/rtems/bar.h
@@ -0,0 +1,39 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+   Contributed by Sebastian Huber <sebastian.huber@embedded-brains.de>.
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This is the RTEMS implementation of a barrier synchronization
+   mechanism for libgomp.  This type is private to the library.  */
+
+#ifndef GOMP_RTEMS_BARRIER_H
+#define GOMP_RTEMS_BARRIER_H 1
+
+#include <sys/lock.h>
+
+typedef struct _Futex_Control gomp_barrier_futex_t;
+
+#define HAVE_BARRIER_FUTEX 1
+
+#include "../linux/bar.h"
+
+#endif /* GOMP_RTEMS_BARRIER_H */
diff --git a/libgomp/config/rtems/mutex.c b/libgomp/config/rtems/mutex.c
new file mode 100644
index 0000000..39bb64d
--- /dev/null
+++ b/libgomp/config/rtems/mutex.c
@@ -0,0 +1 @@
+/* Everything is in the header.  */
diff --git a/libgomp/config/rtems/mutex.h b/libgomp/config/rtems/mutex.h
new file mode 100644
index 0000000..39901ee
--- /dev/null
+++ b/libgomp/config/rtems/mutex.h
@@ -0,0 +1,57 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+   Contributed by Sebastian Huber <sebastian.huber@embedded-brains.de>.
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This is the RTEMS implementation of a mutex synchronization
+   mechanism for libgomp.  This type is private to the library.  */
+
+#ifndef GOMP_MUTEX_H
+#define GOMP_MUTEX_H 1
+
+#include <sys/lock.h>
+
+typedef struct _Mutex_Control gomp_mutex_t;
+
+#define GOMP_MUTEX_INIT_0 1
+
+static inline void gomp_mutex_init (gomp_mutex_t *mutex)
+{
+  _Mutex_Initialize (mutex);
+}
+
+static inline void gomp_mutex_lock (gomp_mutex_t *mutex)
+{
+  _Mutex_Acquire (mutex);
+}
+
+static inline void gomp_mutex_unlock (gomp_mutex_t *mutex)
+{
+  _Mutex_Release (mutex);
+}
+
+static inline void gomp_mutex_destroy (gomp_mutex_t *mutex)
+{
+  _Mutex_Destroy (mutex);
+}
+
+#endif /* GOMP_MUTEX_H */
diff --git a/libgomp/config/rtems/sem.c b/libgomp/config/rtems/sem.c
new file mode 100644
index 0000000..39bb64d
--- /dev/null
+++ b/libgomp/config/rtems/sem.c
@@ -0,0 +1 @@
+/* Everything is in the header.  */
diff --git a/libgomp/config/rtems/sem.h b/libgomp/config/rtems/sem.h
new file mode 100644
index 0000000..0d6765b
--- /dev/null
+++ b/libgomp/config/rtems/sem.h
@@ -0,0 +1,55 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+   Contributed by Sebastian Huber <sebastian.huber@embedded-brains.de>.
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This is the RTEMS implementation of a semaphore synchronization
+   mechanism for libgomp.  This type is private to the library.  */
+
+#ifndef GOMP_SEM_H
+#define GOMP_SEM_H 1
+
+#include <sys/lock.h>
+
+typedef struct _Semaphore_Control gomp_sem_t;
+
+static inline void gomp_sem_init (gomp_sem_t *sem, int value)
+{
+  _Semaphore_Initialize (sem, (unsigned int) value);
+}
+
+static inline void gomp_sem_wait (gomp_sem_t *sem)
+{
+  _Semaphore_Wait (sem);
+}
+
+static inline void gomp_sem_post (gomp_sem_t *sem)
+{
+  _Semaphore_Post (sem);
+}
+
+static inline void gomp_sem_destroy (gomp_sem_t *sem)
+{
+  _Semaphore_Destroy (sem);
+}
+
+#endif /* GOMP_SEM_H  */
diff --git a/libgomp/configure b/libgomp/configure
index f1a92ba..a42e6bb 100755
--- a/libgomp/configure
+++ b/libgomp/configure
@@ -15338,6 +15338,23 @@ $as_echo "#define HAVE_BROKEN_POSIX_SEMAPHORES 1" >>confdefs.h
     ;;
 esac
 
+# RTEMS specific checks
+case "$host" in
+  *-*-rtems*)
+    ac_fn_c_check_type "$LINENO" "struct _Mutex_Control" "ac_cv_type_struct__Mutex_Control" "#include <sys/lock.h>
+"
+if test "x$ac_cv_type_struct__Mutex_Control" = x""yes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_STRUCT__MUTEX_CONTROL 1
+_ACEOF
+
+
+fi
+
+    ;;
+esac
+
  # Check whether --enable-linux-futex was given.
 if test "${enable_linux_futex+set}" = set; then :
   enableval=$enable_linux_futex;
diff --git a/libgomp/configure.ac b/libgomp/configure.ac
index 9cf0218..461845e 100644
--- a/libgomp/configure.ac
+++ b/libgomp/configure.ac
@@ -213,6 +213,13 @@ case "$host" in
     ;;
 esac
 
+# RTEMS specific checks
+case "$host" in
+  *-*-rtems*)
+    AC_CHECK_TYPES([struct _Mutex_Control],[],[],[#include <sys/lock.h>])
+    ;;
+esac
+
 GCC_LINUX_FUTEX(:)
 
 # Check for pthread_{,attr_}[sg]etaffinity_np.
diff --git a/libgomp/configure.tgt b/libgomp/configure.tgt
index 2970f6f..25ec7fc 100644
--- a/libgomp/configure.tgt
+++ b/libgomp/configure.tgt
@@ -151,6 +151,13 @@ case "${target}" in
 	XLDFLAGS="${XLDFLAGS} -lpthread"
 	;;
 
+  *-*-rtems*)
+	# Use self-contained synchronization objects if provided by Newlib
+	if test "x$ac_cv_type_struct__Mutex_Control" = xyes ; then
+	    config_path="rtems posix"
+	fi
+	;;
+
   *)
 	;;
 
-- 
1.8.4.5


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