1 /* 2 * Spin and read/write lock operations. 3 * 4 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM 5 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM 6 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM 7 * Rework to support virtual processors 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License 11 * as published by the Free Software Foundation; either version 12 * 2 of the License, or (at your option) any later version. 13 */ 14 15 #include <linux/kernel.h> 16 #include <linux/spinlock.h> 17 #include <linux/export.h> 18 #include <linux/stringify.h> 19 #include <linux/smp.h> 20 21 /* waiting for a spinlock... */ 22 #if defined(CONFIG_PPC_SPLPAR) 23 #include <asm/hvcall.h> 24 #include <asm/smp.h> 25 26 void __spin_yield(arch_spinlock_t *lock) 27 { 28 unsigned int lock_value, holder_cpu, yield_count; 29 30 lock_value = lock->slock; 31 if (lock_value == 0) 32 return; 33 holder_cpu = lock_value & 0xffff; 34 BUG_ON(holder_cpu >= NR_CPUS); 35 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 36 if ((yield_count & 1) == 0) 37 return; /* virtual cpu is currently running */ 38 rmb(); 39 if (lock->slock != lock_value) 40 return; /* something has changed */ 41 plpar_hcall_norets(H_CONFER, 42 get_hard_smp_processor_id(holder_cpu), yield_count); 43 } 44 45 /* 46 * Waiting for a read lock or a write lock on a rwlock... 47 * This turns out to be the same for read and write locks, since 48 * we only know the holder if it is write-locked. 49 */ 50 void __rw_yield(arch_rwlock_t *rw) 51 { 52 int lock_value; 53 unsigned int holder_cpu, yield_count; 54 55 lock_value = rw->lock; 56 if (lock_value >= 0) 57 return; /* no write lock at present */ 58 holder_cpu = lock_value & 0xffff; 59 BUG_ON(holder_cpu >= NR_CPUS); 60 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 61 if ((yield_count & 1) == 0) 62 return; /* virtual cpu is currently running */ 63 rmb(); 64 if (rw->lock != lock_value) 65 return; /* something has changed */ 66 plpar_hcall_norets(H_CONFER, 67 get_hard_smp_processor_id(holder_cpu), yield_count); 68 } 69 #endif 70 71 void arch_spin_unlock_wait(arch_spinlock_t *lock) 72 { 73 smp_mb(); 74 75 while (lock->slock) { 76 HMT_low(); 77 if (SHARED_PROCESSOR) 78 __spin_yield(lock); 79 } 80 HMT_medium(); 81 82 smp_mb(); 83 } 84 85 EXPORT_SYMBOL(arch_spin_unlock_wait); 86