[gomp] Reuse futex barrier implementation for RTEMS

[Sebastian Huber]

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?

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/futex.h b/libgomp/config/linux/futex.h
index c99ea37..7aab595 100644
--- a/libgomp/config/linux/futex.h
+++ b/libgomp/config/linux/futex.h
@@ -68,3 +68,7 @@ cpu_relax (void)
  {
    __asm volatile ("" : : : "memory");
  }
+
+#define barrier_futex_wait(addr, val, futex) futex_wait (addr, val)
+
+#define barrier_futex_wake(addr, count, futex) futex_wake (addr, count)
diff --git a/libgomp/config/linux/bar.c b/libgomp/config/linux/bar.c
index 51fbd99..d776796 100644
--- a/libgomp/config/linux/bar.c
+++ b/libgomp/config/linux/bar.c
@@ -40,7 +40,7 @@ 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
      {
@@ -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;
      }
      }
@@ -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;
      }
      }
@@ -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);
  }

-- 
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 geschäftliche Mitteilung im Sinne des EHUG.