rom/exec/allocsignal.c

   1 /*
   2     Copyright © 1995-2015, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Allocate a signal
   6     Lang: english
   7 */
   8
   9 #include <exec/execbase.h>
  10 #include <exec/tasks.h>
  11 #include <aros/libcall.h>
  12 #include <proto/exec.h>
  13
  14 #include "exec_util.h"
  15 #if defined(__AROSEXEC_SMP__)
  16 #include "etask.h"
  17 #endif
  18
  19 /*****************************************************************************
  20
  21     NAME */
  22
  23         AROS_LH1(BYTE, AllocSignal,
  24
  25 /*  SYNOPSIS */
  26         AROS_LHA(LONG, signalNum, D0),
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 55, Exec)
  30
  31 /*  FUNCTION
  32         Allocate a given signal out of the current task's pool of signals.
  33         Every task has a set of signals to communicate with other tasks.
  34         Half of them are reserved for the system and half of them are
  35         free for general use. Some of the reserved signals (e.g.
  36         SIGBREAKF_CTRL_C) have a defined behaviour and may be used by user
  37         code, however.
  38
  39         You must not allocate or free signals from exception handlers.
  40
  41     INPUTS
  42         signalNum - Number of the signal to allocate or -1 if any signal
  43                     will do.
  44
  45     RESULT
  46         Number of the signal or -1 if the signal couldn't be allocated.
  47
  48     NOTES
  49
  50     EXAMPLE
  51
  52     BUGS
  53
  54     SEE ALSO
  55         FreeSignal(), Signal(), Wait()
  56
  57     INTERNALS
  58
  59 ******************************************************************************/
  60 {
  61     AROS_LIBFUNC_INIT
  62
  63     /* Cast signalNum to BYTE for AOS/68k compatibility. Apps may set up only D0.b */
  64     return AllocTaskSignal(GET_THIS_TASK, (BYTE)signalNum, SysBase);
  65
  66     AROS_LIBFUNC_EXIT
  67 } /* AllocSignal() */
  68
  69 LONG AllocTaskSignal(struct Task *ThisTask, LONG signalNum, struct ExecBase *SysBase)
  70 {
  71     ULONG mask;
  72     ULONG mask1;
  73
  74     mask = ThisTask->tc_SigAlloc;
  75
  76     /* Will any signal do? */
  77     if(signalNum < 0)
  78     {
  79         /*
  80          * To get the last nonzero bit in a number I use a&~a+1:
  81          * Given a number that ends with a row of zeros  xxxx1000
  82          * I first toggle all bits in that number        XXXX0111
  83          * then add 1 to toggle all but the last 0 again XXXX1000
  84          * and AND this with the original number         00001000
  85          *
  86          * And since ~a+1=-a I can use a&-a instead.
  87          *
  88          * And to get the last zero bit I finally use ~a&-~a.
  89          */
  90         mask1 = ~mask & - ~mask;
  91
  92         /* Is the bit already allocated? */
  93         if(mask1 == 0)
  94             return -1;
  95
  96         /* And get the bit number */
  97         signalNum=(mask1&0xffff0000?16:0)+(mask1&0xff00ff00?8:0)+
  98                   (mask1&0xf0f0f0f0? 4:0)+(mask1&0xcccccccc?2:0)+
  99                   (mask1&0xaaaaaaaa? 1:0);
 100     }
 101     else
 102     {
 103         mask1 = 1L << signalNum;
 104
 105         /* If signal bit is already allocated, return. */
 106         if(ThisTask->tc_SigAlloc & mask1)
 107             return -1;
 108     }
 109
 110     /*
 111      *  I shouldn't need to disable around changing the signal masks
 112      *  because the only thing allowed to change the mask of allocated,
 113      *  excepting and waiting signals is the task itself. On the other
 114      *  hand, I need to use Disable around the received signals because it
 115      *  can be modified by interrupts, and I cannot rely upon the below
 116      *  being atomic.
 117      */
 118
 119     ThisTask->tc_SigAlloc  |=  mask1;
 120     ThisTask->tc_SigExcept &= ~mask1;
 121     ThisTask->tc_SigWait   &= ~mask1;
 122
 123 #if defined(__AROSEXEC_SMP__)
 124     EXEC_SPINLOCK_LOCK(&IntETask(ThisTask->tc_UnionETask.tc_ETask)->iet_TaskLock, SPINLOCK_MODE_WRITE);
 125 #endif
 126     Disable();
 127
 128     ThisTask->tc_SigRecvd  &= ~mask1;
 129
 130 #if defined(__AROSEXEC_SMP__)
 131     EXEC_SPINLOCK_UNLOCK(&IntETask(ThisTask->tc_UnionETask.tc_ETask)->iet_TaskLock);
 132 #endif
 133     Enable();
 134
 135     return signalNum;
 136 }