summaryrefslogtreecommitdiff
path: root/libpthread/linuxthreads/sysdeps/i386/pspinlock.c
diff options
context:
space:
mode:
Diffstat (limited to 'libpthread/linuxthreads/sysdeps/i386/pspinlock.c')
-rw-r--r--libpthread/linuxthreads/sysdeps/i386/pspinlock.c103
1 files changed, 103 insertions, 0 deletions
diff --git a/libpthread/linuxthreads/sysdeps/i386/pspinlock.c b/libpthread/linuxthreads/sysdeps/i386/pspinlock.c
new file mode 100644
index 000000000..e4ec24a0b
--- /dev/null
+++ b/libpthread/linuxthreads/sysdeps/i386/pspinlock.c
@@ -0,0 +1,103 @@
+/* POSIX spinlock implementation. x86 version.
+ Copyright (C) 2000, 2002, 2006 Free Software Foundation, Inc.
+ 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 Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser 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>
+#include "internals.h"
+#include <kernel-features.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
+ ("\n"
+ "1:\n\t"
+ "lock; decl %0\n\t"
+ "js 2f\n\t"
+ ".section .text.spinlock,\"ax\"\n"
+ "2:\n\t"
+ "cmpl $0,%0\n\t"
+ "rep; nop\n\t"
+ "jle 2b\n\t"
+ "jmp 1b\n\t"
+ ".previous"
+ : "=m" (*lock));
+ return 0;
+}
+weak_alias (__pthread_spin_lock, pthread_spin_lock)
+
+
+int
+__pthread_spin_trylock (pthread_spinlock_t *lock)
+{
+ int oldval;
+
+ asm volatile
+ ("xchgl %0,%1"
+ : "=r" (oldval), "=m" (*lock)
+ : "0" (0));
+ return oldval > 0 ? 0 : EBUSY;
+}
+weak_alias (__pthread_spin_trylock, pthread_spin_trylock)
+
+
+int
+__pthread_spin_unlock (pthread_spinlock_t *lock)
+{
+ asm volatile
+ ("movl $1,%0"
+ : "=m" (*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 = 1;
+ 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)
+
+#ifndef __ASSUME_SET_THREAD_AREA_SYSCALL
+int __have_no_set_thread_area;
+#endif