| yuezonghe | 824eb0c | 2024-06-27 02:32:26 -0700 | [diff] [blame] | 1 | /* POSIX spinlock implementation. Alpha version. |
| 2 | Copyright (C) 2000 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public License as |
| 7 | published by the Free Software Foundation; either version 2.1 of the |
| 8 | License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; see the file COPYING.LIB. If not, |
| 17 | write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| 18 | Boston, MA 02111-1307, USA. */ |
| 19 | |
| 20 | #include <errno.h> |
| 21 | #include <pthread.h> |
| 22 | #include "internals.h" |
| 23 | |
| 24 | |
| 25 | /* This implementation is similar to the one used in the Linux kernel. |
| 26 | But the kernel is byte instructions for the memory access. This is |
| 27 | faster but unusable here. The problem is that only 128 |
| 28 | threads/processes could use the spinlock at the same time. If (by |
| 29 | a design error in the program) a thread/process would hold the |
| 30 | spinlock for a time long enough to accumulate 128 waiting |
| 31 | processes, the next one will find a positive value in the spinlock |
| 32 | and assume it is unlocked. We cannot accept that. */ |
| 33 | |
| 34 | int |
| 35 | __pthread_spin_lock (pthread_spinlock_t *lock) |
| 36 | { |
| 37 | unsigned int tmp; |
| 38 | __asm__ __volatile__ |
| 39 | ("1: ldl_l %0,%1\n" |
| 40 | " blbs %0,2f\n" |
| 41 | " or %0,1,%0\n" |
| 42 | " stl_c %0,%1\n" |
| 43 | " beq %0,2f\n" |
| 44 | " mb\n" |
| 45 | ".subsection 2\n" |
| 46 | "2: ldl %0,%1\n" |
| 47 | " blbs %0,2b\n" |
| 48 | " br 1b\n" |
| 49 | ".previous" |
| 50 | : "=r" (tmp), "=m" (lock) |
| 51 | : "m" (lock)); |
| 52 | return 0; |
| 53 | } |
| 54 | weak_alias (__pthread_spin_lock, pthread_spin_lock) |
| 55 | |
| 56 | |
| 57 | int |
| 58 | __pthread_spin_trylock (pthread_spinlock_t *lock) |
| 59 | { |
| 60 | unsigned long int oldval; |
| 61 | unsigned long int temp; |
| 62 | |
| 63 | __asm__ __volatile__ |
| 64 | ("1: ldl_l %0,%1\n" |
| 65 | " and %0,%3,%2\n" |
| 66 | " bne %2,2f\n" |
| 67 | " xor %0,%3,%0\n" |
| 68 | " stl_c %0,%1\n" |
| 69 | " beq %0,3f\n" |
| 70 | " mb\n" |
| 71 | "2:\n" |
| 72 | ".subsection 2\n" |
| 73 | "3: br 1b\n" |
| 74 | ".previous" |
| 75 | : "=&r" (temp), "=m" (*lock), "=&r" (oldval) |
| 76 | : "Ir" (1UL), "m" (*lock)); |
| 77 | |
| 78 | return oldval == 0 ? 0 : EBUSY; |
| 79 | } |
| 80 | weak_alias (__pthread_spin_trylock, pthread_spin_trylock) |
| 81 | |
| 82 | |
| 83 | int |
| 84 | __pthread_spin_unlock (pthread_spinlock_t *lock) |
| 85 | { |
| 86 | __asm__ __volatile__ ("mb"); |
| 87 | return *lock = 0; |
| 88 | } |
| 89 | weak_alias (__pthread_spin_unlock, pthread_spin_unlock) |
| 90 | |
| 91 | |
| 92 | int |
| 93 | __pthread_spin_init (pthread_spinlock_t *lock, int pshared) |
| 94 | { |
| 95 | /* We can ignore the `pshared' parameter. Since we are busy-waiting |
| 96 | all processes which can access the memory location `lock' points |
| 97 | to can use the spinlock. */ |
| 98 | *lock = 0; |
| 99 | return 0; |
| 100 | } |
| 101 | weak_alias (__pthread_spin_init, pthread_spin_init) |
| 102 | |
| 103 | |
| 104 | int |
| 105 | __pthread_spin_destroy (pthread_spinlock_t *lock) |
| 106 | { |
| 107 | /* Nothing to do. */ |
| 108 | return 0; |
| 109 | } |
| 110 | weak_alias (__pthread_spin_destroy, pthread_spin_destroy) |