| /* POSIX spinlock implementation. Alpha version. |
| Copyright (C) 2000 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" |
| |
| |
| /* 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) |
| { |
| unsigned int tmp; |
| __asm__ __volatile__ |
| ("1: ldl_l %0,%1\n" |
| " blbs %0,2f\n" |
| " or %0,1,%0\n" |
| " stl_c %0,%1\n" |
| " beq %0,2f\n" |
| " mb\n" |
| ".subsection 2\n" |
| "2: ldl %0,%1\n" |
| " blbs %0,2b\n" |
| " br 1b\n" |
| ".previous" |
| : "=r" (tmp), "=m" (lock) |
| : "m" (lock)); |
| return 0; |
| } |
| weak_alias (__pthread_spin_lock, pthread_spin_lock) |
| |
| |
| int |
| __pthread_spin_trylock (pthread_spinlock_t *lock) |
| { |
| unsigned long int oldval; |
| unsigned long int temp; |
| |
| __asm__ __volatile__ |
| ("1: ldl_l %0,%1\n" |
| " and %0,%3,%2\n" |
| " bne %2,2f\n" |
| " xor %0,%3,%0\n" |
| " stl_c %0,%1\n" |
| " beq %0,3f\n" |
| " mb\n" |
| "2:\n" |
| ".subsection 2\n" |
| "3: br 1b\n" |
| ".previous" |
| : "=&r" (temp), "=m" (*lock), "=&r" (oldval) |
| : "Ir" (1UL), "m" (*lock)); |
| |
| return oldval == 0 ? 0 : EBUSY; |
| } |
| weak_alias (__pthread_spin_trylock, pthread_spin_trylock) |
| |
| |
| int |
| __pthread_spin_unlock (pthread_spinlock_t *lock) |
| { |
| __asm__ __volatile__ ("mb"); |
| return *lock = 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) |