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