arch/all-pc/kernel/spinunlock.c

   1 /*
   2     Copyright © 2017, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include <asm/cpu.h>
   7 #include <aros/atomic.h>
   8 #include <aros/types/spinlock_s.h>
   9 #include <aros/kernel.h>
  10 #include <aros/libcall.h>
  11
  12 #include <kernel_base.h>
  13 #include <kernel_debug.h>
  14
  15 #include <proto/kernel.h>
  16
  17 #define D(x)
  18
  19 AROS_LH1(void, KrnSpinUnLock,
  20         AROS_LHA(spinlock_t *, lock, A0),
  21         struct KernelBase *, KernelBase, 53, Kernel)
  22 {
  23     AROS_LIBFUNC_INIT
  24
  25     D(bug("[Kernel] %s(0x%p)\n", __func__, lock));
  26
  27     lock->s_Owner = NULL;
  28     /*
  29     use cmpxchg - expect SPINLOCKF_WRITE and replace it with 0 (unlocking the spinlock), if that succeeded, the lock
  30     was in WRITE mode and is now free. If that was not the case, continue with unlocking READ mode spinlock
  31     */
  32     if (!compare_and_exchange_long((ULONG*)&lock->lock, SPINLOCKF_WRITE, 0, NULL))
  33     {
  34         /*
  35         Unlocking READ mode spinlock means we need to put it into UDPATING state, decrement counter and unlock from
  36         UPDATING state.
  37         */
  38         while (!compare_and_exchange_byte((UBYTE*)&lock->block[3], 0, SPINLOCKF_UPDATING >> 24, NULL))
  39         {
  40             // Tell CPU we are spinning
  41             asm volatile("pause");
  42         }
  43
  44         // Just in case someone tries to unlock already unlocked stuff
  45         if (lock->slock.readcount != 0)
  46         {
  47             lock->slock.readcount--;
  48         }
  49 #if defined(AROS_NO_ATOMIC_OPERATIONS)
  50         lock->slock.updating = 0;
  51 #else
  52         __AROS_ATOMIC_AND_L(lock->lock, ~SPINLOCKF_UPDATING);
  53 #endif
  54     }
  55
  56     D(bug("[Kernel] %s: lock = %08x\n", __func__, lock->lock));
  57
  58     return;
  59
  60     AROS_LIBFUNC_EXIT
  61 }