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/export.h> 18 #include <linux/smp.h> 19 20 /* waiting for a spinlock... */ 21 #if defined(CONFIG_PPC_SPLPAR) 22 #include <asm/hvcall.h> 23 #include <asm/smp.h> 24 25 void __spin_yield(arch_spinlock_t *lock) 26 { 27 unsigned int lock_value, holder_cpu, yield_count; 28 29 lock_value = lock->slock; 30 if (lock_value == 0) 31 return; 32 holder_cpu = lock_value & 0xffff; 33 BUG_ON(holder_cpu >= NR_CPUS); 34 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 35 if ((yield_count & 1) == 0) 36 return; /* virtual cpu is currently running */ 37 rmb(); 38 if (lock->slock != lock_value) 39 return; /* something has changed */ 40 plpar_hcall_norets(H_CONFER, 41 get_hard_smp_processor_id(holder_cpu), yield_count); 42 } 43 EXPORT_SYMBOL_GPL(__spin_yield); 44 45 /* 46 * Waiting for a read lock or a write lock on a rwlock... 47 * This turns out to be the same for read and write locks, since 48 * we only know the holder if it is write-locked. 49 */ 50 void __rw_yield(arch_rwlock_t *rw) 51 { 52 int lock_value; 53 unsigned int holder_cpu, yield_count; 54 55 lock_value = rw->lock; 56 if (lock_value >= 0) 57 return; /* no write lock at present */ 58 holder_cpu = lock_value & 0xffff; 59 BUG_ON(holder_cpu >= NR_CPUS); 60 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 61 if ((yield_count & 1) == 0) 62 return; /* virtual cpu is currently running */ 63 rmb(); 64 if (rw->lock != lock_value) 65 return; /* something has changed */ 66 plpar_hcall_norets(H_CONFER, 67 get_hard_smp_processor_id(holder_cpu), yield_count); 68 } 69 #endif 70