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 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 yield_count = lppaca[holder_cpu].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 62 lock_value = rw->lock; 63 if (lock_value >= 0) 64 return; /* no write lock at present */ 65 holder_cpu = lock_value & 0xffff; 66 BUG_ON(holder_cpu >= NR_CPUS); 67 yield_count = lppaca[holder_cpu].yield_count; 68 if ((yield_count & 1) == 0) 69 return; /* virtual cpu is currently running */ 70 rmb(); 71 if (rw->lock != lock_value) 72 return; /* something has changed */ 73 #ifdef CONFIG_PPC_ISERIES 74 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 75 ((u64)holder_cpu << 32) | yield_count); 76 #else 77 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu), 78 yield_count); 79 #endif 80 } 81 #endif 82 83 void __raw_spin_unlock_wait(raw_spinlock_t *lock) 84 { 85 while (lock->slock) { 86 HMT_low(); 87 if (SHARED_PROCESSOR) 88 __spin_yield(lock); 89 } 90 HMT_medium(); 91 } 92 93 EXPORT_SYMBOL(__raw_spin_unlock_wait); 94