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/config.h> 16 #include <linux/kernel.h> 17 #include <linux/spinlock.h> 18 #include <linux/module.h> 19 #include <linux/stringify.h> 20 #include <linux/smp.h> 21 22 /* waiting for a spinlock... */ 23 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES) 24 #include <asm/hvcall.h> 25 #include <asm/iseries/hv_call.h> 26 27 void __spin_yield(raw_spinlock_t *lock) 28 { 29 unsigned int lock_value, holder_cpu, yield_count; 30 struct paca_struct *holder_paca; 31 32 lock_value = lock->slock; 33 if (lock_value == 0) 34 return; 35 holder_cpu = lock_value & 0xffff; 36 BUG_ON(holder_cpu >= NR_CPUS); 37 holder_paca = &paca[holder_cpu]; 38 yield_count = holder_paca->lppaca.yield_count; 39 if ((yield_count & 1) == 0) 40 return; /* virtual cpu is currently running */ 41 rmb(); 42 if (lock->slock != lock_value) 43 return; /* something has changed */ 44 #ifdef CONFIG_PPC_ISERIES 45 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 46 ((u64)holder_cpu << 32) | yield_count); 47 #else 48 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu), 49 yield_count); 50 #endif 51 } 52 53 /* 54 * Waiting for a read lock or a write lock on a rwlock... 55 * This turns out to be the same for read and write locks, since 56 * we only know the holder if it is write-locked. 57 */ 58 void __rw_yield(raw_rwlock_t *rw) 59 { 60 int lock_value; 61 unsigned int holder_cpu, yield_count; 62 struct paca_struct *holder_paca; 63 64 lock_value = rw->lock; 65 if (lock_value >= 0) 66 return; /* no write lock at present */ 67 holder_cpu = lock_value & 0xffff; 68 BUG_ON(holder_cpu >= NR_CPUS); 69 holder_paca = &paca[holder_cpu]; 70 yield_count = holder_paca->lppaca.yield_count; 71 if ((yield_count & 1) == 0) 72 return; /* virtual cpu is currently running */ 73 rmb(); 74 if (rw->lock != lock_value) 75 return; /* something has changed */ 76 #ifdef CONFIG_PPC_ISERIES 77 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 78 ((u64)holder_cpu << 32) | yield_count); 79 #else 80 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu), 81 yield_count); 82 #endif 83 } 84 #endif 85 86 void __raw_spin_unlock_wait(raw_spinlock_t *lock) 87 { 88 while (lock->slock) { 89 HMT_low(); 90 if (SHARED_PROCESSOR) 91 __spin_yield(lock); 92 } 93 HMT_medium(); 94 } 95 96 EXPORT_SYMBOL(__raw_spin_unlock_wait); 97