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 #include <asm/smp.h> 27 28 void __spin_yield(raw_spinlock_t *lock) 29 { 30 unsigned int lock_value, holder_cpu, yield_count; 31 struct paca_struct *holder_paca; 32 33 lock_value = lock->slock; 34 if (lock_value == 0) 35 return; 36 holder_cpu = lock_value & 0xffff; 37 BUG_ON(holder_cpu >= NR_CPUS); 38 holder_paca = &paca[holder_cpu]; 39 yield_count = holder_paca->lppaca.yield_count; 40 if ((yield_count & 1) == 0) 41 return; /* virtual cpu is currently running */ 42 rmb(); 43 if (lock->slock != lock_value) 44 return; /* something has changed */ 45 #ifdef CONFIG_PPC_ISERIES 46 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 47 ((u64)holder_cpu << 32) | yield_count); 48 #else 49 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu), 50 yield_count); 51 #endif 52 } 53 54 /* 55 * Waiting for a read lock or a write lock on a rwlock... 56 * This turns out to be the same for read and write locks, since 57 * we only know the holder if it is write-locked. 58 */ 59 void __rw_yield(raw_rwlock_t *rw) 60 { 61 int lock_value; 62 unsigned int holder_cpu, yield_count; 63 struct paca_struct *holder_paca; 64 65 lock_value = rw->lock; 66 if (lock_value >= 0) 67 return; /* no write lock at present */ 68 holder_cpu = lock_value & 0xffff; 69 BUG_ON(holder_cpu >= NR_CPUS); 70 holder_paca = &paca[holder_cpu]; 71 yield_count = holder_paca->lppaca.yield_count; 72 if ((yield_count & 1) == 0) 73 return; /* virtual cpu is currently running */ 74 rmb(); 75 if (rw->lock != lock_value) 76 return; /* something has changed */ 77 #ifdef CONFIG_PPC_ISERIES 78 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 79 ((u64)holder_cpu << 32) | yield_count); 80 #else 81 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu), 82 yield_count); 83 #endif 84 } 85 #endif 86 87 void __raw_spin_unlock_wait(raw_spinlock_t *lock) 88 { 89 while (lock->slock) { 90 HMT_low(); 91 if (SHARED_PROCESSOR) 92 __spin_yield(lock); 93 } 94 HMT_medium(); 95 } 96 97 EXPORT_SYMBOL(__raw_spin_unlock_wait); 98