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locks.c

/*
 * 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
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/smp.h>

/* waiting for a spinlock... */
#if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
#include <asm/hvcall.h>
#include <asm/iseries/hv_call.h>
#include <asm/smp.h>
#include <asm/firmware.h>

void __spin_yield(raw_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 = lppaca[holder_cpu].yield_count;
      if ((yield_count & 1) == 0)
            return;           /* virtual cpu is currently running */
      rmb();
      if (lock->slock != lock_value)
            return;           /* something has changed */
      if (firmware_has_feature(FW_FEATURE_ISERIES))
            HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
                  ((u64)holder_cpu << 32) | yield_count);
#ifdef CONFIG_PPC_SPLPAR
      else
            plpar_hcall_norets(H_CONFER,
                  get_hard_smp_processor_id(holder_cpu), yield_count);
#endif
}

/*
 * 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 __rw_yield(raw_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 = lppaca[holder_cpu].yield_count;
      if ((yield_count & 1) == 0)
            return;           /* virtual cpu is currently running */
      rmb();
      if (rw->lock != lock_value)
            return;           /* something has changed */
      if (firmware_has_feature(FW_FEATURE_ISERIES))
            HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
                  ((u64)holder_cpu << 32) | yield_count);
#ifdef CONFIG_PPC_SPLPAR
      else
            plpar_hcall_norets(H_CONFER,
                  get_hard_smp_processor_id(holder_cpu), yield_count);
#endif
}
#endif

void __raw_spin_unlock_wait(raw_spinlock_t *lock)
{
      while (lock->slock) {
            HMT_low();
            if (SHARED_PROCESSOR)
                  __spin_yield(lock);
      }
      HMT_medium();
}

EXPORT_SYMBOL(__raw_spin_unlock_wait);

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