| yuezonghe | 824eb0c | 2024-06-27 02:32:26 -0700 | [diff] [blame] | 1 | /* POSIX spinlock implementation. S/390 version. |
| 2 | Copyright (C) 2000, 2004 Free Software Foundation, Inc. |
| 3 | Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com). |
| 4 | This file is part of the GNU C Library. |
| 5 | |
| 6 | The GNU C Library is free software; you can redistribute it and/or |
| 7 | modify it under the terms of the GNU Lesser General Public License as |
| 8 | published by the Free Software Foundation; either version 2.1 of the |
| 9 | License, or (at your option) any later version. |
| 10 | |
| 11 | The GNU C Library is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | Lesser General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU Lesser General Public |
| 17 | License along with the GNU C Library; see the file COPYING.LIB. If not, |
| 18 | write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| 19 | Boston, MA 02111-1307, USA. */ |
| 20 | |
| 21 | #include <errno.h> |
| 22 | #include <pthread.h> |
| 23 | #include "internals.h" |
| 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 | __asm__ __volatile__(" basr 1,0\n" |
| 38 | "0: slr 0,0\n" |
| 39 | " cs 0,1,%1\n" |
| 40 | " jl 0b\n" |
| 41 | : "=m" (*lock) |
| 42 | : "m" (*lock) : "0", "1", "cc" ); |
| 43 | return 0; |
| 44 | } |
| 45 | weak_alias (__pthread_spin_lock, pthread_spin_lock) |
| 46 | |
| 47 | int |
| 48 | __pthread_spin_trylock (pthread_spinlock_t *lock) |
| 49 | { |
| 50 | int oldval; |
| 51 | |
| 52 | __asm__ __volatile__(" slr %1,%1\n" |
| 53 | " basr 1,0\n" |
| 54 | "0: cs %1,1,%0" |
| 55 | : "=m" (*lock), "=&d" (oldval) |
| 56 | : "m" (*lock) : "1", "cc" ); |
| 57 | return oldval == 0 ? 0 : EBUSY; |
| 58 | } |
| 59 | weak_alias (__pthread_spin_trylock, pthread_spin_trylock) |
| 60 | |
| 61 | |
| 62 | int |
| 63 | __pthread_spin_unlock (pthread_spinlock_t *lock) |
| 64 | { |
| 65 | __asm__ __volatile__(" xc 0(4,%0),0(%0)\n" |
| 66 | " bcr 15,0" |
| 67 | : : "a" (lock) : "memory" ); |
| 68 | return 0; |
| 69 | } |
| 70 | weak_alias (__pthread_spin_unlock, pthread_spin_unlock) |
| 71 | |
| 72 | |
| 73 | int |
| 74 | __pthread_spin_init (pthread_spinlock_t *lock, int pshared) |
| 75 | { |
| 76 | /* We can ignore the `pshared' parameter. Since we are busy-waiting |
| 77 | all processes which can access the memory location `lock' points |
| 78 | to can use the spinlock. */ |
| 79 | *lock = 0; |
| 80 | return 0; |
| 81 | } |
| 82 | weak_alias (__pthread_spin_init, pthread_spin_init) |
| 83 | |
| 84 | |
| 85 | int |
| 86 | __pthread_spin_destroy (pthread_spinlock_t *lock) |
| 87 | { |
| 88 | /* Nothing to do. */ |
| 89 | return 0; |
| 90 | } |
| 91 | weak_alias (__pthread_spin_destroy, pthread_spin_destroy) |