linux/arch/powerpc/lib/locks.c
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   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
  28void __spin_yield(arch_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_of(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#ifdef CONFIG_PPC_SPLPAR
  47        else
  48                plpar_hcall_norets(H_CONFER,
  49                        get_hard_smp_processor_id(holder_cpu), yield_count);
  50#endif
  51}
  52
  53/*
  54 * Waiting for a read lock or a write lock on a rwlock...
  55 * This turns out to be the same for read and write locks, since
  56 * we only know the holder if it is write-locked.
  57 */
  58void __rw_yield(arch_rwlock_t *rw)
  59{
  60        int lock_value;
  61        unsigned int holder_cpu, yield_count;
  62
  63        lock_value = rw->lock;
  64        if (lock_value >= 0)
  65                return;         /* no write lock at present */
  66        holder_cpu = lock_value & 0xffff;
  67        BUG_ON(holder_cpu >= NR_CPUS);
  68        yield_count = lppaca_of(holder_cpu).yield_count;
  69        if ((yield_count & 1) == 0)
  70                return;         /* virtual cpu is currently running */
  71        rmb();
  72        if (rw->lock != lock_value)
  73                return;         /* something has changed */
  74        if (firmware_has_feature(FW_FEATURE_ISERIES))
  75                HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
  76                        ((u64)holder_cpu << 32) | yield_count);
  77#ifdef CONFIG_PPC_SPLPAR
  78        else
  79                plpar_hcall_norets(H_CONFER,
  80                        get_hard_smp_processor_id(holder_cpu), yield_count);
  81#endif
  82}
  83#endif
  84
  85void arch_spin_unlock_wait(arch_spinlock_t *lock)
  86{
  87        while (lock->slock) {
  88                HMT_low();
  89                if (SHARED_PROCESSOR)
  90                        __spin_yield(lock);
  91        }
  92        HMT_medium();
  93}
  94
  95EXPORT_SYMBOL(arch_spin_unlock_wait);
  96