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         struct paca_struct *holder_paca;
  32
  33         lock_value = lock->slock;
  34         if (lock_value == 0)
  35                 return;
  36         holder_cpu = lock_value & 0xffff;
  37         BUG_ON(holder_cpu >= NR_CPUS);
  38         holder_paca = &paca[holder_cpu];
  39         yield_count = holder_paca->lppaca.yield_count;
  40         if ((yield_count & 1) == 0)
  41                 return;         /* virtual cpu is currently running */
  42         rmb();
  43         if (lock->slock != lock_value)
  44                 return;         /* something has changed */
  45 #ifdef CONFIG_PPC_ISERIES
  46         HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
  47                 ((u64)holder_cpu << 32) | yield_count);
  48 #else
  49         plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
  50                            yield_count);
  51 #endif
  52 }
  53
  54 /*
  55  * Waiting for a read lock or a write lock on a rwlock...
  56  * This turns out to be the same for read and write locks, since
  57  * we only know the holder if it is write-locked.
  58  */
  59 void __rw_yield(raw_rwlock_t *rw)
  60 {
  61         int lock_value;
  62         unsigned int holder_cpu, yield_count;
  63         struct paca_struct *holder_paca;
  64
  65         lock_value = rw->lock;
  66         if (lock_value >= 0)
  67                 return;         /* no write lock at present */
  68         holder_cpu = lock_value & 0xffff;
  69         BUG_ON(holder_cpu >= NR_CPUS);
  70         holder_paca = &paca[holder_cpu];
  71         yield_count = holder_paca->lppaca.yield_count;
  72         if ((yield_count & 1) == 0)
  73                 return;         /* virtual cpu is currently running */
  74         rmb();
  75         if (rw->lock != lock_value)
  76                 return;         /* something has changed */
  77 #ifdef CONFIG_PPC_ISERIES
  78         HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
  79                 ((u64)holder_cpu << 32) | yield_count);
  80 #else
  81         plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
  82                            yield_count);
  83 #endif
  84 }
  85 #endif
  86
  87 void __raw_spin_unlock_wait(raw_spinlock_t *lock)
  88 {
  89         while (lock->slock) {
  90                 HMT_low();
  91                 if (SHARED_PROCESSOR)
  92                         __spin_yield(lock);
  93         }
  94         HMT_medium();
  95 }
  96
  97 EXPORT_SYMBOL(__raw_spin_unlock_wait);