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(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  */
  58 void __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
  85 void 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
  95 EXPORT_SYMBOL(arch_spin_unlock_wait);