arch/arm-native/kernel/spinunlock.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 <kernel_base.h>
  11
  12 #include <proto/kernel.h>
  13
  14 AROS_LH1(void, KrnSpinUnLock,
  15         AROS_LHA(spinlock_t *, lock, A0),
  16         struct KernelBase *, KernelBase, 44, Kernel)
  17 {
  18     AROS_LIBFUNC_INIT
  19
  20     if (lock->lock == 0)
  21         return;
  22
  23     /*
  24      * Are we releasing a write lock? Just zero out the value. Also send event so that other cores waiting for lock
  25      * wake up.
  26      */
  27     if (lock->lock & 0x80000000)
  28     {
  29         lock->lock = 0;
  30         asm volatile("sev");
  31     }
  32     else
  33     {
  34         unsigned long lock_value, write_result;
  35
  36         asm volatile(
  37                 "1:     ldrex   %0, [%2]        \n\t"   // Read lock value and gain write exclusive lock
  38                 "       sub     %0, %0, #1      \n\t"   // Decrease lock value
  39                 "       strex   %1, %0, [%2]    \n\t"   // Try to update the lock value
  40                 "       teq     %1, #0          \n\t"   // test if write succeeded
  41                 "       bne     1b              \n\t"   // Try again if write failed
  42                 :"=&r"(lock_value), "=&r"(write_result)
  43                 :"r"(&lock->lock)
  44                 :"cc"
  45         );
  46
  47         /* Send event to other cores if lock is free */
  48         if (lock_value == 0)
  49             asm volatile("sev");
  50     }
  51
  52     AROS_LIBFUNC_EXIT
  53 }