arch/ppc/lib/locks.c

   1 /*
   2  * $Id: locks.c,v 1.25 1999/09/10 10:40:13 davem Exp $
   3  *
   4  * Locks for smp ppc
   5  *
   6  * Written by Cort Dougan (cort@cs.nmt.edu)
   7  */
   8
   9
  10 #include <linux/kernel.h>
  11 #include <linux/sched.h>
  12 #include <linux/delay.h>
  13 #include <linux/spinlock.h>
  14 #include <asm/processor.h>
  15 #include <asm/system.h>
  16 #include <asm/io.h>
  17
  18 #define DEBUG_LOCKS 1
  19
  20 #undef INIT_STUCK
  21 #define INIT_STUCK 200000000 /*0xffffffff*/
  22
  23 void _spin_lock(spinlock_t *lock)
  24 {
  25         int cpu = smp_processor_id();
  26 #ifdef DEBUG_LOCKS
  27         unsigned int stuck = INIT_STUCK;
  28 #endif /* DEBUG_LOCKS */
  29         while (__spin_trylock(&lock->lock)) {
  30 #ifdef DEBUG_LOCKS
  31                 if(!--stuck) {
  32                         printk("_spin_lock(%p) CPU#%d NIP %p"
  33                                " holder: cpu %ld pc %08lX\n",
  34                                lock, cpu, __builtin_return_address(0),
  35                                lock->owner_cpu,lock->owner_pc);
  36                         stuck = INIT_STUCK;
  37                         /* steal the lock */
  38                         /*xchg_u32((void *)&lock->lock,0);*/
  39                 }
  40 #endif /* DEBUG_LOCKS */
  41         }
  42         lock->owner_pc = (unsigned long)__builtin_return_address(0);
  43         lock->owner_cpu = cpu;
  44 }
  45
  46 int spin_trylock(spinlock_t *lock)
  47 {
  48         if (__spin_trylock(&lock->lock))
  49                 return 0;
  50         lock->owner_cpu = smp_processor_id();
  51         lock->owner_pc = (unsigned long)__builtin_return_address(0);
  52         return 1;
  53 }
  54
  55
  56
  57 void _spin_unlock(spinlock_t *lp)
  58 {
  59 #ifdef DEBUG_LOCKS
  60         if ( !lp->lock )
  61                 printk("_spin_unlock(%p): no lock cpu %d %s/%d\n", lp,
  62                       smp_processor_id(),current->comm,current->pid);
  63         if ( lp->owner_cpu != smp_processor_id() )
  64                 printk("_spin_unlock(%p): cpu %d trying clear of cpu %d pc %lx val %lx\n",
  65                       lp, smp_processor_id(), (int)lp->owner_cpu,
  66                       lp->owner_pc,lp->lock);
  67 #endif /* DEBUG_LOCKS */
  68         lp->owner_pc = lp->owner_cpu = 0;
  69         wmb();
  70         lp->lock = 0;
  71         wmb();
  72 }
  73
  74 /*
  75  * Just like x86, implement read-write locks as a 32-bit counter
  76  * with the high bit (sign) being the "write" bit.
  77  * -- Cort
  78  */
  79 void _read_lock(rwlock_t *rw)
  80 {
  81 #ifdef DEBUG_LOCKS
  82         unsigned long stuck = INIT_STUCK;
  83         int cpu = smp_processor_id();
  84 #endif /* DEBUG_LOCKS */
  85
  86 again:
  87         /* get our read lock in there */
  88         wmb();
  89         atomic_inc((atomic_t *) &(rw)->lock);
  90         if ( (signed long)((rw)->lock) < 0) /* someone has a write lock */
  91         {
  92                 /* turn off our read lock */
  93                 atomic_dec((atomic_t *) &(rw)->lock);
  94                 /* wait for the write lock to go away */
  95                 while ((signed long)((rw)->lock) < 0)
  96                 {
  97 #ifdef DEBUG_LOCKS
  98                         if(!--stuck)
  99                         {
 100                                 printk("_read_lock(%p) CPU#%d\n", rw, cpu);
 101                                 stuck = INIT_STUCK;
 102                         }
 103 #endif /* DEBUG_LOCKS */
 104                 }
 105                 /* try to get the read lock again */
 106                 goto again;
 107         }
 108         wmb();
 109 }
 110
 111 void _read_unlock(rwlock_t *rw)
 112 {
 113 #ifdef DEBUG_LOCKS
 114         if ( rw->lock == 0 )
 115                 printk("_read_unlock(): %s/%d (nip %08lX) lock %lx\n",
 116                        current->comm,current->pid,current->thread.regs->nip,
 117                       rw->lock);
 118 #endif /* DEBUG_LOCKS */
 119         wmb();
 120         atomic_dec((atomic_t *) &(rw)->lock);
 121         wmb();
 122 }
 123
 124 void _write_lock(rwlock_t *rw)
 125 {
 126 #ifdef DEBUG_LOCKS
 127         unsigned long stuck = INIT_STUCK;
 128         int cpu = smp_processor_id();
 129 #endif /* DEBUG_LOCKS */
 130
 131 again:
 132         wmb();
 133         if ( test_and_set_bit(31,&(rw)->lock) ) /* someone has a write lock */
 134         {
 135                 while ( (rw)->lock & (1<<31) ) /* wait for write lock */
 136                 {
 137 #ifdef DEBUG_LOCKS
 138                         if(!--stuck)
 139                         {
 140                                 printk("write_lock(%p) CPU#%d lock %lx)\n",
 141                                        rw, cpu,rw->lock);
 142                                 stuck = INIT_STUCK;
 143                         }
 144 #endif /* DEBUG_LOCKS */
 145                         barrier();
 146                 }
 147                 goto again;
 148         }
 149
 150         if ( (rw)->lock & ~(1<<31)) /* someone has a read lock */
 151         {
 152                 /* clear our write lock and wait for reads to go away */
 153                 clear_bit(31,&(rw)->lock);
 154                 while ( (rw)->lock & ~(1<<31) )
 155                 {
 156 #ifdef DEBUG_LOCKS
 157                         if(!--stuck)
 158                         {
 159                                 printk("write_lock(%p) 2 CPU#%d lock %lx)\n",
 160                                        rw, cpu,rw->lock);
 161                                 stuck = INIT_STUCK;
 162                         }
 163 #endif /* DEBUG_LOCKS */
 164                         barrier();
 165                 }
 166                 goto again;
 167         }
 168         wmb();
 169 }
 170
 171 void _write_unlock(rwlock_t *rw)
 172 {
 173 #ifdef DEBUG_LOCKS
 174         if ( !(rw->lock & (1<<31)) )
 175                 printk("_write_lock(): %s/%d (nip %08lX) lock %lx\n",
 176                       current->comm,current->pid,current->thread.regs->nip,
 177                       rw->lock);
 178 #endif /* DEBUG_LOCKS */
 179         wmb();
 180         clear_bit(31,&(rw)->lock);
 181         wmb();
 182 }
 183
 184 void __lock_kernel(struct task_struct *task)
 185 {
 186 #ifdef DEBUG_LOCKS
 187         unsigned long stuck = INIT_STUCK;
 188
 189         if ( (signed long)(task->lock_depth) < 0 )
 190         {
 191                 printk("__lock_kernel(): %s/%d (nip %08lX) lock depth %x\n",
 192                       task->comm,task->pid,task->thread.regs->nip,
 193                       task->lock_depth);
 194         }
 195 #endif /* DEBUG_LOCKS */
 196
 197         if (atomic_inc_return((atomic_t *) &task->lock_depth) != 1)
 198                 return;
 199         /* mine! */
 200         while (__spin_trylock(&klock_info.kernel_flag)) {
 201 #ifdef DEBUG_LOCKS
 202                 if(!--stuck) {
 203                         printk("_lock_kernel() CPU#%d NIP %p\n",
 204                                smp_processor_id(),
 205                                __builtin_return_address(0));
 206                         stuck = INIT_STUCK;
 207                 }
 208 #endif /* DEBUG_LOCKS */
 209         }
 210
 211         klock_info.akp = smp_processor_id();
 212         /* my kernel mode! mine!!! */
 213 }
 214
 215 void __unlock_kernel(struct task_struct *task)
 216 {
 217 #ifdef DEBUG_LOCKS
 218         if ((task->lock_depth == 0) || (klock_info.kernel_flag != KLOCK_HELD))
 219         {
 220                 printk("__unlock_kernel(): %s/%d (nip %08lX) "
 221                        "lock depth %x flags %lx\n",
 222                        task->comm,task->pid,task->thread.regs->nip,
 223                        task->lock_depth, klock_info.kernel_flag);
 224                 klock_info.akp = NO_PROC_ID;
 225                 klock_info.kernel_flag = 0;
 226                 return;
 227         }
 228 #endif /* DEBUG_LOCKS */
 229         if (atomic_dec_and_test((atomic_t *) &task->lock_depth))
 230         {
 231                 wmb();
 232                 klock_info.akp = NO_PROC_ID;
 233                 wmb();
 234                 klock_info.kernel_flag = KLOCK_CLEAR;
 235                 wmb();
 236         }
 237 }
 238
 239 void reacquire_kernel_lock(struct task_struct *task, int cpu,int depth)
 240 {
 241         if (depth)
 242         {
 243                 __cli();
 244                 __lock_kernel(task);
 245                 task->lock_depth = depth;
 246                 __sti();
 247         }
 248 }