rom/kernel/spinlock.c

   1 /*
   2     Copyright © 2015-2017, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc:
   6 */
   7
   8 #include <aros/types/spinlock_s.h>
   9 #include <aros/kernel.h>
  10 #include <aros/libcall.h>
  11 #include <utility/hooks.h>
  12
  13 #include <kernel_base.h>
  14
  15 /*****************************************************************************
  16
  17     NAME */
  18 #include <proto/kernel.h>
  19
  20         AROS_LH3(spinlock_t *, KrnSpinLock,
  21
  22 /*  SYNOPSIS */
  23         AROS_LHA(spinlock_t *, lock, A1),
  24         AROS_LHA(struct Hook *, failhook, A0),
  25         AROS_LHA(ULONG, mode, D0),
  26
  27 /*  LOCATION */
  28         struct KernelBase *, KernelBase, 52, Kernel)
  29
  30 /*  FUNCTION
  31
  32     INPUTS
  33         lock      - spinlock to lock
  34         failhook  - called if the lock is already held
  35         mode      - type of lock to obtain.
  36
  37     RESULT
  38         returns a pointer to the spinlock "handle".
  39
  40     NOTES
  41         The failhook is necessary, because it is not safe
  42         for code running in user space to spin on a shared lock.
  43         If a lower priority task holds the lock, it will never be released.
  44            Because of  this, Exec uses a hook that puts the task on
  45            a spinning list, to allow other code to run until the lock is
  46            released.  At this point the "spinning" task will wake and
  47            obtain the lock.
  48
  49     EXAMPLE
  50
  51     BUGS
  52
  53     SEE ALSO
  54
  55     INTERNALS
  56
  57 ******************************************************************************/
  58 {
  59     AROS_LIBFUNC_INIT
  60
  61     /* The implementation of this function is architecture-specific */
  62     return lock;
  63
  64     AROS_LIBFUNC_EXIT
  65 }