| // SPDX-License-Identifier: GPL-2.0-or-later | |
| /* | |
| * Spin and read/write lock operations. | |
| * | |
| * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM | |
| * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM | |
| * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM | |
| * Rework to support virtual processors | |
| */ | |
| #include <linux/kernel.h> | |
| #include <linux/spinlock.h> | |
| #include <linux/export.h> | |
| #include <linux/smp.h> | |
| /* waiting for a spinlock... */ | |
| #if defined(CONFIG_PPC_SPLPAR) | |
| #include <asm/hvcall.h> | |
| #include <asm/smp.h> | |
| void splpar_spin_yield(arch_spinlock_t *lock) | |
| { | |
| unsigned int lock_value, holder_cpu, yield_count; | |
| lock_value = lock->slock; | |
| if (lock_value == 0) | |
| return; | |
| holder_cpu = lock_value & 0xffff; | |
| BUG_ON(holder_cpu >= NR_CPUS); | |
| yield_count = yield_count_of(holder_cpu); | |
| if ((yield_count & 1) == 0) | |
| return; /* virtual cpu is currently running */ | |
| rmb(); | |
| if (lock->slock != lock_value) | |
| return; /* something has changed */ | |
| yield_to_preempted(holder_cpu, yield_count); | |
| } | |
| EXPORT_SYMBOL_GPL(splpar_spin_yield); | |
| /* | |
| * Waiting for a read lock or a write lock on a rwlock... | |
| * This turns out to be the same for read and write locks, since | |
| * we only know the holder if it is write-locked. | |
| */ | |
| void splpar_rw_yield(arch_rwlock_t *rw) | |
| { | |
| int lock_value; | |
| unsigned int holder_cpu, yield_count; | |
| lock_value = rw->lock; | |
| if (lock_value >= 0) | |
| return; /* no write lock at present */ | |
| holder_cpu = lock_value & 0xffff; | |
| BUG_ON(holder_cpu >= NR_CPUS); | |
| yield_count = yield_count_of(holder_cpu); | |
| if ((yield_count & 1) == 0) | |
| return; /* virtual cpu is currently running */ | |
| rmb(); | |
| if (rw->lock != lock_value) | |
| return; /* something has changed */ | |
| yield_to_preempted(holder_cpu, yield_count); | |
| } | |
| #endif |