1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Spin and read/write lock operations. 4 * 5 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM 6 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM 7 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM 8 * Rework to support virtual processors 9 */ 10 11 #include <linux/kernel.h> 12 #include <linux/spinlock.h> 13 #include <linux/export.h> 14 #include <linux/smp.h> 15 16 /* waiting for a spinlock... */ 17 #if defined(CONFIG_PPC_SPLPAR) 18 #include <asm/hvcall.h> 19 #include <asm/smp.h> 20 21 void splpar_spin_yield(arch_spinlock_t *lock) 22 { 23 unsigned int lock_value, holder_cpu, yield_count; 24 25 lock_value = lock->slock; 26 if (lock_value == 0) 27 return; 28 holder_cpu = lock_value & 0xffff; 29 BUG_ON(holder_cpu >= NR_CPUS); 30 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 31 if ((yield_count & 1) == 0) 32 return; /* virtual cpu is currently running */ 33 rmb(); 34 if (lock->slock != lock_value) 35 return; /* something has changed */ 36 plpar_hcall_norets(H_CONFER, 37 get_hard_smp_processor_id(holder_cpu), yield_count); 38 } 39 EXPORT_SYMBOL_GPL(splpar_spin_yield); 40 41 /* 42 * Waiting for a read lock or a write lock on a rwlock... 43 * This turns out to be the same for read and write locks, since 44 * we only know the holder if it is write-locked. 45 */ 46 void splpar_rw_yield(arch_rwlock_t *rw) 47 { 48 int lock_value; 49 unsigned int holder_cpu, yield_count; 50 51 lock_value = rw->lock; 52 if (lock_value >= 0) 53 return; /* no write lock at present */ 54 holder_cpu = lock_value & 0xffff; 55 BUG_ON(holder_cpu >= NR_CPUS); 56 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); 57 if ((yield_count & 1) == 0) 58 return; /* virtual cpu is currently running */ 59 rmb(); 60 if (rw->lock != lock_value) 61 return; /* something has changed */ 62 plpar_hcall_norets(H_CONFER, 63 get_hard_smp_processor_id(holder_cpu), yield_count); 64 } 65 #endif 66