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8497695243
arch_spin_lock_wait_flags() checks if a spinlock is not held before
trying a compare and swap instruction. If the lock is unlocked it
tries the compare and swap instruction, however if a different cpu
grabbed the lock in the meantime the instruction will fail as
expected.
Subsequently the arch_spin_lock_wait_flags() incorrectly tries to
figure out if the cpu that holds the lock is running. However it is
using the wrong cpu number for this (-1) and then will also yield the
current cpu to the wrong cpu.
Fix this by adding a missing continue statement.
Fixes: 470ada6b1a ("s390/spinlock: refactor arch_spin_lock_wait[_flags]")
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
293 lines
6.3 KiB
C
293 lines
6.3 KiB
C
/*
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* Out of line spinlock code.
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*
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* Copyright IBM Corp. 2004, 2006
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*/
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <asm/io.h>
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int spin_retry = -1;
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static int __init spin_retry_init(void)
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{
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if (spin_retry < 0)
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spin_retry = MACHINE_HAS_CAD ? 10 : 1000;
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return 0;
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}
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early_initcall(spin_retry_init);
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/**
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* spin_retry= parameter
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*/
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static int __init spin_retry_setup(char *str)
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{
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spin_retry = simple_strtoul(str, &str, 0);
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return 1;
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}
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__setup("spin_retry=", spin_retry_setup);
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static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
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{
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asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
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}
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static inline int cpu_is_preempted(int cpu)
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{
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if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
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return 0;
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if (smp_vcpu_scheduled(cpu))
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return 0;
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return 1;
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}
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void arch_spin_lock_wait(arch_spinlock_t *lp)
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{
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unsigned int cpu = SPINLOCK_LOCKVAL;
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unsigned int owner;
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int count, first_diag;
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first_diag = 1;
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while (1) {
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owner = ACCESS_ONCE(lp->lock);
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/* Try to get the lock if it is free. */
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if (!owner) {
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if (_raw_compare_and_swap(&lp->lock, 0, cpu))
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return;
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continue;
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}
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/* First iteration: check if the lock owner is running. */
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if (first_diag && cpu_is_preempted(~owner)) {
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smp_yield_cpu(~owner);
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first_diag = 0;
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continue;
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}
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/* Loop for a while on the lock value. */
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count = spin_retry;
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do {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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owner = ACCESS_ONCE(lp->lock);
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} while (owner && count-- > 0);
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if (!owner)
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continue;
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/*
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* For multiple layers of hypervisors, e.g. z/VM + LPAR
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* yield the CPU unconditionally. For LPAR rely on the
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* sense running status.
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*/
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if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
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smp_yield_cpu(~owner);
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first_diag = 0;
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}
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}
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}
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EXPORT_SYMBOL(arch_spin_lock_wait);
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void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
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{
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unsigned int cpu = SPINLOCK_LOCKVAL;
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unsigned int owner;
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int count, first_diag;
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local_irq_restore(flags);
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first_diag = 1;
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while (1) {
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owner = ACCESS_ONCE(lp->lock);
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/* Try to get the lock if it is free. */
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if (!owner) {
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local_irq_disable();
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if (_raw_compare_and_swap(&lp->lock, 0, cpu))
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return;
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local_irq_restore(flags);
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continue;
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}
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/* Check if the lock owner is running. */
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if (first_diag && cpu_is_preempted(~owner)) {
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smp_yield_cpu(~owner);
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first_diag = 0;
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continue;
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}
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/* Loop for a while on the lock value. */
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count = spin_retry;
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do {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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owner = ACCESS_ONCE(lp->lock);
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} while (owner && count-- > 0);
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if (!owner)
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continue;
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/*
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* For multiple layers of hypervisors, e.g. z/VM + LPAR
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* yield the CPU unconditionally. For LPAR rely on the
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* sense running status.
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*/
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if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
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smp_yield_cpu(~owner);
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first_diag = 0;
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}
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}
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}
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EXPORT_SYMBOL(arch_spin_lock_wait_flags);
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int arch_spin_trylock_retry(arch_spinlock_t *lp)
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{
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unsigned int cpu = SPINLOCK_LOCKVAL;
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unsigned int owner;
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int count;
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for (count = spin_retry; count > 0; count--) {
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owner = ACCESS_ONCE(lp->lock);
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/* Try to get the lock if it is free. */
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if (!owner) {
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if (_raw_compare_and_swap(&lp->lock, 0, cpu))
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return 1;
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} else if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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}
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return 0;
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}
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EXPORT_SYMBOL(arch_spin_trylock_retry);
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void _raw_read_lock_wait(arch_rwlock_t *rw)
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{
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unsigned int owner, old;
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int count = spin_retry;
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#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
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__RAW_LOCK(&rw->lock, -1, __RAW_OP_ADD);
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#endif
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owner = 0;
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while (1) {
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if (count-- <= 0) {
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if (owner && cpu_is_preempted(~owner))
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smp_yield_cpu(~owner);
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count = spin_retry;
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}
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old = ACCESS_ONCE(rw->lock);
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owner = ACCESS_ONCE(rw->owner);
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if ((int) old < 0) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, old, old + 1))
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return;
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}
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}
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EXPORT_SYMBOL(_raw_read_lock_wait);
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int _raw_read_trylock_retry(arch_rwlock_t *rw)
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{
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unsigned int old;
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int count = spin_retry;
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while (count-- > 0) {
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old = ACCESS_ONCE(rw->lock);
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if ((int) old < 0) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, old, old + 1))
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(_raw_read_trylock_retry);
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#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
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void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
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{
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unsigned int owner, old;
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int count = spin_retry;
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owner = 0;
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while (1) {
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if (count-- <= 0) {
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if (owner && cpu_is_preempted(~owner))
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smp_yield_cpu(~owner);
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count = spin_retry;
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}
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old = ACCESS_ONCE(rw->lock);
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owner = ACCESS_ONCE(rw->owner);
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smp_mb();
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if ((int) old >= 0) {
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prev = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
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old = prev;
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}
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if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
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break;
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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}
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}
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EXPORT_SYMBOL(_raw_write_lock_wait);
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#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
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void _raw_write_lock_wait(arch_rwlock_t *rw)
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{
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unsigned int owner, old, prev;
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int count = spin_retry;
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prev = 0x80000000;
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owner = 0;
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while (1) {
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if (count-- <= 0) {
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if (owner && cpu_is_preempted(~owner))
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smp_yield_cpu(~owner);
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count = spin_retry;
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}
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old = ACCESS_ONCE(rw->lock);
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owner = ACCESS_ONCE(rw->owner);
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if ((int) old >= 0 &&
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_raw_compare_and_swap(&rw->lock, old, old | 0x80000000))
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prev = old;
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else
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smp_mb();
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if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
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break;
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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}
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}
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EXPORT_SYMBOL(_raw_write_lock_wait);
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#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
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int _raw_write_trylock_retry(arch_rwlock_t *rw)
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{
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unsigned int old;
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int count = spin_retry;
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while (count-- > 0) {
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old = ACCESS_ONCE(rw->lock);
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if (old) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(_raw_write_trylock_retry);
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void arch_lock_relax(unsigned int cpu)
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{
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if (!cpu)
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return;
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if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
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return;
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smp_yield_cpu(~cpu);
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}
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EXPORT_SYMBOL(arch_lock_relax);
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