arch/arm-native/kernel/spintrylock.c

   1 /*
   2     Copyright © 2015, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include <aros/types/spinlock_s.h>
   7 #include <aros/kernel.h>
   8 #include <aros/libcall.h>
   9
  10 #include <asm/arm/cpu.h>
  11
  12 #include <kernel_base.h>
  13
  14 #include <proto/kernel.h>
  15
  16 AROS_LH2(spinlock_t *, KrnSpinTryLock,
  17         AROS_LHA(spinlock_t *, lock, A0),
  18         AROS_LHA(ULONG, mode, D0),
  19         struct KernelBase *, KernelBase, 42, Kernel)
  20 {
  21     AROS_LIBFUNC_INIT
  22
  23     unsigned long lock_value, tmp;
  24
  25     if (mode == SPINLOCK_MODE_WRITE)
  26     {
  27         do
  28         {
  29             asm volatile(
  30                     "       ldrex   %0, [%2]        \n\t"   // Load the lock value and gain exclusive lock to memory
  31                     "       teq     %0, #0          \n\t"   // is the value 0? It means the lock was free
  32                     "       strexeq %1, %3, [%2]    \n\t"   // Store value to memory and check if it succeeded
  33                     : "=&r"(lock_value), "=&r"(tmp)
  34                     : "r" (&lock->lock), "r"(0x80000000), "1"(0)
  35                     : "cc"
  36             );
  37         } while(tmp);
  38
  39         if (lock_value == 0)
  40         {
  41             dmb();
  42             return lock;
  43         }
  44         else
  45             return NULL;
  46     }
  47     else
  48     {
  49         do
  50         {
  51             asm volatile(
  52                     "       ldrex   %0, [%2]        \n\t"   // Load lock value and gain exclusive lock to memory
  53                     "       adds    %0, %0, #1      \n\t"   // Increase the lock value and update conditional bits
  54                     "       strexpl %1, %0, [%2]    \n\t"   // Store value to memory if positive and check result
  55                     : "=&r"(lock_value), "=&r"(tmp)
  56                     : "r"(&lock->lock), "1"(0)
  57                     : "cc"
  58             );
  59         } while(tmp);
  60
  61         if (lock_value < 0x80000000)
  62         {
  63             dmb();
  64             return lock;
  65         }
  66         else
  67             return NULL;
  68     }
  69
  70     AROS_LIBFUNC_EXIT
  71 }