minix/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 "kernel/system.h"
  11 #include <assert.h>
  12
  13 #if USE_RUNCTL
  14
  15 /*===========================================================================*
  16  *                                do_runctl                                  *
  17  *===========================================================================*/
  18 int do_runctl(struct proc * caller, message * m_ptr)
  19 {
  20 /* Control a process's RTS_PROC_STOP flag. Used for process management.
  21  * If the process is queued sending a message or stopped for system call
  22  * tracing, and the RC_DELAY request flag is given, set MF_SIG_DELAY instead
  23  * of RTS_PROC_STOP, and send a SIGSNDELAY signal later when the process is done
  24  * sending (ending the delay). Used by PM for safe signal delivery.
  25  */
  26   int proc_nr, action, flags;
  27   register struct proc *rp;
  28
  29   /* Extract the message parameters and do sanity checking. */
  30   if (!isokendpt(m_ptr->RC_ENDPT, &proc_nr)) return(EINVAL);
  31   if (iskerneln(proc_nr)) return(EPERM);
  32   rp = proc_addr(proc_nr);
  33
  34   action = m_ptr->RC_ACTION;
  35   flags = m_ptr->RC_FLAGS;
  36
  37   /* Is the target sending or syscall-traced? Then set MF_SIG_DELAY instead.
  38    * Do this only when the RC_DELAY flag is set in the request flags field.
  39    * The process will not become runnable before PM has called SYS_ENDKSIG.
  40    * Note that asynchronous messages are not covered: a process using SENDA
  41    * should not also install signal handlers *and* expect POSIX compliance.
  42    */
  43
  44   if (action == RC_STOP && (flags & RC_DELAY)) {
  45         if (RTS_ISSET(rp, RTS_SENDING) || (rp->p_misc_flags & MF_SC_DEFER))
  46                 rp->p_misc_flags |= MF_SIG_DELAY;
  47
  48         if (rp->p_misc_flags & MF_SIG_DELAY)
  49                 return (EBUSY);
  50   }
  51
  52   /* Either set or clear the stop flag. */
  53   switch (action) {
  54   case RC_STOP:
  55 #if CONFIG_SMP
  56           /* check if we must stop a process on a different CPU */
  57           if (rp->p_cpu != cpuid) {
  58                   smp_schedule_stop_proc(rp);
  59                   break;
  60           }
  61 #endif
  62           RTS_SET(rp, RTS_PROC_STOP);
  63         break;
  64   case RC_RESUME:
  65         assert(RTS_ISSET(rp, RTS_PROC_STOP));
  66         RTS_UNSET(rp, RTS_PROC_STOP);
  67         break;
  68   default:
  69         return(EINVAL);
  70   }
  71
  72   return(OK);
  73 }
  74
  75 #endif /* USE_RUNCTL */
  76