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 #include <asm/firmware.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 if (firmware_has_feature(FW_FEATURE_ISERIES)) 44 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 45 ((u64)holder_cpu << 32) | yield_count); 46 else 47 plpar_hcall_norets(H_CONFER, 48 get_hard_smp_processor_id(holder_cpu), yield_count); 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 if (firmware_has_feature(FW_FEATURE_ISERIES)) 73 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc, 74 ((u64)holder_cpu << 32) | yield_count); 75 else 76 plpar_hcall_norets(H_CONFER, 77 get_hard_smp_processor_id(holder_cpu), yield_count); 78 } 79 #endif 80 81 void __raw_spin_unlock_wait(raw_spinlock_t *lock) 82 { 83 while (lock->slock) { 84 HMT_low(); 85 if (SHARED_PROCESSOR) 86 __spin_yield(lock); 87 } 88 HMT_medium(); 89 } 90 91 EXPORT_SYMBOL(__raw_spin_unlock_wait); 92