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