Linux/S390 POSIX spinlock implementation.

linuxthreads/sysdeps/s390/pspinlock.c

@@ -0,0 +1,91 @@
+/* POSIX spinlock implementation.  S/390 version.
+   Copyright (C) 2000 Free Software Foundation, Inc.
+   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <errno.h>
+#include <pthread.h>
+
+
+/* This implementation is similar to the one used in the Linux kernel.
+   But the kernel is byte instructions for the memory access.  This is
+   faster but unusable here.  The problem is that only 128
+   threads/processes could use the spinlock at the same time.  If (by
+   a design error in the program) a thread/process would hold the
+   spinlock for a time long enough to accumulate 128 waiting
+   processes, the next one will find a positive value in the spinlock
+   and assume it is unlocked.  We cannot accept that.  */
+
+int
+__pthread_spin_lock (pthread_spinlock_t *lock)
+{
+  asm volatile("    basr  1,0\n"
+	       "0:  slr   0,0\n"
+	       "    cs    0,1,%1\n"
+	       "    jl    0b\n"
+	       : "=m" (*lock)
+	       : "0" (*lock) : "0", "1", "cc" );
+  return 0;
+}
+weak_alias (__pthread_spin_lock, pthread_spin_lock)
+
+int
+__pthread_spin_trylock (pthread_spinlock_t *lock)
+{
+  int oldval;
+
+  asm volatile("    slr   %1,%1\n"
+	       "    basr  1,0\n"
+	       "0:  cs    %1,1,%0"
+	       : "=m" (*lock), "=&d" (oldval)
+	       : "0" (*lock) : "1", "cc" );
+  return oldval == 0 ? 0 : EBUSY;
+}
+weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
+
+
+int
+__pthread_spin_unlock (pthread_spinlock_t *lock)
+{
+  asm volatile("    xc 0(4,%0),0(%0)\n"
+	       "    bcr 15,0"
+	       : "=a" (lock) );
+  return 0;
+}
+weak_alias (__pthread_spin_unlock, pthread_spin_unlock)
+
+
+int
+__pthread_spin_init (pthread_spinlock_t *lock, int pshared)
+{
+  /* We can ignore the `pshared' parameter.  Since we are busy-waiting
+     all processes which can access the memory location `lock' points
+     to can use the spinlock.  */
+  *lock = 0;
+  return 0;
+}
+weak_alias (__pthread_spin_init, pthread_spin_init)
+
+
+int
+__pthread_spin_destroy (pthread_spinlock_t *lock)
+{
+  /* Nothing to do.  */
+  return 0;
+}
+weak_alias (__pthread_spin_destroy, pthread_spin_destroy)