arch/powerpc/lib/locks.c

   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/config.h>
  16 #include <linux/kernel.h>
  17 #include <linux/spinlock.h>
  18 #include <linux/module.h>
  19 #include <linux/stringify.h>
  20 #include <linux/smp.h>
  21
  22 /* waiting for a spinlock... */
  23 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
  24 #include <asm/hvcall.h>
  25 #include <asm/iseries/hv_call.h>
  26 #include <asm/smp.h>
  27
  28 void __spin_yield(raw_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[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 #ifdef CONFIG_PPC_ISERIES
  44         HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
  45                 ((u64)holder_cpu << 32) | yield_count);
  46 #else
  47         plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
  48                            yield_count);
  49 #endif
  50 }
  51
  52 /*
  53  * Waiting for a read lock or a write lock on a rwlock...
  54  * This turns out to be the same for read and write locks, since
  55  * we only know the holder if it is write-locked.
  56  */
  57 void __rw_yield(raw_rwlock_t *rw)
  58 {
  59         int lock_value;
  60         unsigned int holder_cpu, yield_count;
  61
  62         lock_value = rw->lock;
  63         if (lock_value >= 0)
  64                 return;         /* no write lock at present */
  65         holder_cpu = lock_value & 0xffff;
  66         BUG_ON(holder_cpu >= NR_CPUS);
  67         yield_count = lppaca[holder_cpu].yield_count;
  68         if ((yield_count & 1) == 0)
  69                 return;         /* virtual cpu is currently running */
  70         rmb();
  71         if (rw->lock != lock_value)
  72                 return;         /* something has changed */
  73 #ifdef CONFIG_PPC_ISERIES
  74         HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
  75                 ((u64)holder_cpu << 32) | yield_count);
  76 #else
  77         plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
  78                            yield_count);
  79 #endif
  80 }
  81 #endif
  82
  83 void __raw_spin_unlock_wait(raw_spinlock_t *lock)
  84 {
  85         while (lock->slock) {
  86                 HMT_low();
  87                 if (SHARED_PROCESSOR)
  88                         __spin_yield(lock);
  89         }
  90         HMT_medium();
  91 }
  92
  93 EXPORT_SYMBOL(__raw_spin_unlock_wait);