kernel/system/do_runctl.c

   1 /* The kernel call implemented in this file:
   2  *   m_type:    SYS_RUNCTL
   3  *
   4  * The parameters for this kernel call are:
   5  *    m1_i1:    RC_ENDPT        process number to control
   6  *    m1_i2:    RC_ACTION       stop or resume the process
   7  *    m1_i3:    RC_FLAGS        request flags
   8  */
   9
  10 #include "../system.h"
  11
  12 #if USE_RUNCTL
  13
  14 /*===========================================================================*
  15  *                                do_runctl                                  *
  16  *===========================================================================*/
  17 PUBLIC int do_runctl(struct proc * caller, message * m_ptr)
  18 {
  19 /* Control a process's RTS_PROC_STOP flag. Used for process management.
  20  * If the process is queued sending a message or stopped for system call
  21  * tracing, and the RC_DELAY request flag is given, set MF_SIG_DELAY instead
  22  * of RTS_PROC_STOP, and send a SIGNDELAY signal later when the process is done
  23  * sending (ending the delay). Used by PM for safe signal delivery.
  24  */
  25   int proc_nr, action, flags, delayed;
  26   register struct proc *rp;
  27
  28   /* Extract the message parameters and do sanity checking. */
  29   if (!isokendpt(m_ptr->RC_ENDPT, &proc_nr)) return(EINVAL);
  30   if (iskerneln(proc_nr)) return(EPERM);
  31   rp = proc_addr(proc_nr);
  32
  33   action = m_ptr->RC_ACTION;
  34   flags = m_ptr->RC_FLAGS;
  35
  36   /* Is the target sending or syscall-traced? Then set MF_SIG_DELAY instead.
  37    * Do this only when the RC_DELAY flag is set in the request flags field.
  38    * The process will not become runnable before PM has called SYS_ENDKSIG.
  39    * Note that asynchronous messages are not covered: a process using SENDA
  40    * should not also install signal handlers *and* expect POSIX compliance.
  41    */
  42   if (action == RC_STOP && (flags & RC_DELAY)) {
  43         RTS_SET(rp, RTS_SYS_LOCK);
  44
  45         if (RTS_ISSET(rp, RTS_SENDING) || (rp->p_misc_flags & MF_SC_DEFER))
  46                 rp->p_misc_flags |= MF_SIG_DELAY;
  47
  48         delayed = (rp->p_misc_flags & MF_SIG_DELAY);
  49
  50         RTS_UNSET(rp, RTS_SYS_LOCK);
  51
  52         if (delayed) return(EBUSY);
  53   }
  54
  55   /* Either set or clear the stop flag. */
  56   switch (action) {
  57   case RC_STOP:
  58         RTS_SET(rp, RTS_PROC_STOP);
  59         break;
  60   case RC_RESUME:
  61         RTS_UNSET(rp, RTS_PROC_STOP);
  62         break;
  63   default:
  64         return(EINVAL);
  65   }
  66
  67   return(OK);
  68 }
  69
  70 #endif /* USE_RUNCTL */
  71