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