scsi.c

基于组件方式开发操作系统的OSKIT源代码

		    *reqp = req->next;
		    wake_up(&wait_for_request);
		}
	    } else {
		SCpnt->request.rq_status = RQ_SCSI_BUSY;
		SCpnt->request.sem = NULL;   /* And no one is waiting for this
					      * to complete */
	    }
            atomic_inc(&SCpnt->host->host_active); 
            SCSI_LOG_MLQUEUE(5, printk("Activating command for device %d (%d)\n", 
                                       SCpnt->target,
                                       atomic_read(&SCpnt->host->host_active)));
	    break;
	}
    }

    SCpnt->use_sg = 0;            /* Reset the scatter-gather flag */
    SCpnt->old_use_sg  = 0;
    SCpnt->transfersize = 0;      /* No default transfer size */
    SCpnt->cmd_len = 0;

    SCpnt->underflow = 0;         /* Do not flag underflow conditions */

    /* Since not everyone seems to set the device info correctly
     * before Scsi_Cmnd gets send out to scsi_do_command, we do it here.
     * FIXME(eric) This doesn't make any sense.
     */
    SCpnt->channel = device->channel;
    SCpnt->lun = device->lun;
    SCpnt->target = device->id;
    SCpnt->state = SCSI_STATE_INITIALIZING;
    SCpnt->owner = SCSI_OWNER_HIGHLEVEL;

    return SCpnt;
}

/*
 * Function:    scsi_release_command
 *
 * Purpose:     Release a command block.
 *
 * Arguments:   SCpnt - command block we are releasing.
 *
 * Notes:       The command block can no longer be used by the caller once
 *              this funciton is called.  This is in effect the inverse
 *              of scsi_allocate_device/scsi_request_queueable.
 */
void
scsi_release_command(Scsi_Cmnd * SCpnt)
{
  SCpnt->request.rq_status = RQ_INACTIVE;
  SCpnt->state = SCSI_STATE_UNUSED;
  SCpnt->owner = SCSI_OWNER_NOBODY;
  atomic_dec(&SCpnt->host->host_active); 

  SCSI_LOG_MLQUEUE(5, printk("Deactivating command for device %d (active=%d, failed=%d)\n", 
                             SCpnt->target,
                             atomic_read(&SCpnt->host->host_active),
                             SCpnt->host->host_failed));
  if( SCpnt->host->host_failed != 0 )
    {
      SCSI_LOG_ERROR_RECOVERY(5, printk("Error handler thread %d %d\n", 
                                 SCpnt->host->in_recovery,
                                 SCpnt->host->eh_active));
    }

  /*
   * If the host is having troubles, then look to see if this was the last
   * command that might have failed.  If so, wake up the error handler.
   */
  if( SCpnt->host->in_recovery
      && !SCpnt->host->eh_active
      && SCpnt->host->host_busy == SCpnt->host->host_failed )
  {
      SCSI_LOG_ERROR_RECOVERY(5, printk("Waking error handler thread (%d)\n",
                                 atomic_read(&SCpnt->host->eh_wait->count)));
      up(SCpnt->host->eh_wait);
  }
}

/*
 * This is inline because we have stack problemes if we recurse to deeply.
 */

inline int internal_cmnd (Scsi_Cmnd * SCpnt)
{
#ifdef DEBUG_DELAY
    unsigned long clock;
#endif
    struct Scsi_Host   * host;
    int                  rtn = 0;
    unsigned long        timeout;

#if DEBUG
    unsigned long *ret = 0;
#ifdef __mips__
    __asm__ __volatile__ ("move\t%0,$31":"=r"(ret));
#else
   ret =  __builtin_return_address(0);
#endif
#endif

    host = SCpnt->host;

    /* Assign a unique nonzero serial_number. */
    if (++serial_number == 0) serial_number = 1;
    SCpnt->serial_number = serial_number;

    /*
     * We will wait MIN_RESET_DELAY clock ticks after the last reset so
     * we can avoid the drive not being ready.
     */
    timeout = host->last_reset + MIN_RESET_DELAY;

    if (host->resetting && time_before(jiffies, timeout)) {
	int ticks_remaining = timeout - jiffies;
	/*
	 * NOTE: This may be executed from within an interrupt
	 * handler!  This is bad, but for now, it'll do.  The irq
	 * level of the interrupt handler has been masked out by the
	 * platform dependent interrupt handling code already, so the
	 * sti() here will not cause another call to the SCSI host's
	 * interrupt handler (assuming there is one irq-level per
	 * host).
	 */
	spin_unlock_irq(&io_request_lock);
	while (--ticks_remaining >= 0) mdelay(1+999/HZ);
	host->resetting = 0;
	spin_lock_irq(&io_request_lock);
    }

    if( host->hostt->use_new_eh_code )
      {
        scsi_add_timer(SCpnt, SCpnt->timeout_per_command, scsi_times_out);
      }
    else
      {
        scsi_add_timer(SCpnt, SCpnt->timeout_per_command, 
                            scsi_old_times_out);
      }

    /*
     * We will use a queued command if possible, otherwise we will emulate the
     * queuing and calling of completion function ourselves.
     */
    SCSI_LOG_MLQUEUE(3,printk("internal_cmnd (host = %d, channel = %d, target = %d, "
	   "command = %p, buffer = %p, \nbufflen = %d, done = %p)\n",
	   SCpnt->host->host_no, SCpnt->channel, SCpnt->target, SCpnt->cmnd,
	   SCpnt->buffer, SCpnt->bufflen, SCpnt->done));

    SCpnt->state = SCSI_STATE_QUEUED;
    SCpnt->owner = SCSI_OWNER_LOWLEVEL;
    if (host->can_queue)
    {
	SCSI_LOG_MLQUEUE(3,printk("queuecommand : routine at %p\n",
                                  host->hostt->queuecommand));
        /*
         * Use the old error handling code if we haven't converted the driver
         * to use the new one yet.  Note - only the new queuecommand variant
         * passes a meaningful return value.
         */
        if( host->hostt->use_new_eh_code )
          {
            rtn = host->hostt->queuecommand (SCpnt, scsi_done);
            if( rtn != 0 )
            {
                scsi_mlqueue_insert(SCpnt, SCSI_MLQUEUE_HOST_BUSY);
            }
          }
        else
          {
            host->hostt->queuecommand (SCpnt, scsi_old_done);
          }
    }
    else
    {
	int temp;

	SCSI_LOG_MLQUEUE(3,printk("command() :  routine at %p\n", host->hostt->command));
	temp = host->hostt->command (SCpnt);
	SCpnt->result = temp;
#ifdef DEBUG_DELAY
	clock = jiffies + 4 * HZ;
	spin_unlock_irq(&io_request_lock);
	while (time_before(jiffies, clock)) barrier();
	spin_lock_irq(&io_request_lock);
	printk("done(host = %d, result = %04x) : routine at %p\n",
	       host->host_no, temp, host->hostt->command);
#endif
        if( host->hostt->use_new_eh_code )
          {
            scsi_done(SCpnt);
          }
        else
          {
            scsi_old_done(SCpnt);
          }
    }
    SCSI_LOG_MLQUEUE(3,printk("leaving internal_cmnd()\n"));
    return rtn;
}

/*
 * scsi_do_cmd sends all the commands out to the low-level driver.  It
 * handles the specifics required for each low level driver - ie queued
 * or non queued.  It also prevents conflicts when different high level
 * drivers go for the same host at the same time.
 */

void scsi_do_cmd (Scsi_Cmnd * SCpnt, const void *cmnd ,
		  void *buffer, unsigned bufflen, void (*done)(Scsi_Cmnd *),
		  int timeout, int retries)
{
    struct Scsi_Host * host = SCpnt->host;
    Scsi_Device      * device = SCpnt->device;
    int mlqueue = 0;

    SCpnt->owner = SCSI_OWNER_MIDLEVEL;

SCSI_LOG_MLQUEUE(4,
    {
	int i;
	int target = SCpnt->target;
	printk ("scsi_do_cmd (host = %d, channel = %d target = %d, "
		"buffer =%p, bufflen = %d, done = %p, timeout = %d, "
		"retries = %d)\n"
		"command : " , host->host_no, SCpnt->channel, target, buffer,
		bufflen, done, timeout, retries);
	for (i = 0; i < 10; ++i)
	    printk ("%02x  ", ((unsigned char *) cmnd)[i]);
	printk("\n");
    });

    if (!host)
    {
	panic ("Invalid or not present host.\n");
    }


    /*
     * We must prevent reentrancy to the lowlevel host driver.  This prevents
     * it - we enter a loop until the host we want to talk to is not busy.
     * Race conditions are prevented, as interrupts are disabled in between the
     * time we check for the host being not busy, and the time we mark it busy
     * ourselves.
     */

    SCpnt->pid = scsi_pid++;

    while (SCSI_BLOCK((Scsi_Device *) NULL, host)) {
	if (in_interrupt()){
		mlqueue = 1;
		break;
	}
    	spin_unlock(&io_request_lock);	/* FIXME!!! */
	SCSI_SLEEP(&host->host_wait, SCSI_BLOCK((Scsi_Device *) NULL, host));
    	spin_lock_irq(&io_request_lock);	/* FIXME!!! */
    }

    if (host->block) host_active = host;

    host->host_busy++;
    device->device_busy++;

    /*
     * Our own function scsi_done (which marks the host as not busy, disables
     * the timeout counter, etc) will be called by us or by the
     * scsi_hosts[host].queuecommand() function needs to also call
     * the completion function for the high level driver.
     */

    memcpy ((void *) SCpnt->data_cmnd , (const void *) cmnd, 12);
    SCpnt->reset_chain = NULL;
    SCpnt->serial_number = 0;
    SCpnt->serial_number_at_timeout = 0;
    SCpnt->bufflen = bufflen;
    SCpnt->buffer = buffer;
    SCpnt->flags = 0;
    SCpnt->retries = 0;
    SCpnt->allowed = retries;
    SCpnt->done = done;
    SCpnt->timeout_per_command = timeout;

    memcpy ((void *) SCpnt->cmnd , (const void *) cmnd, 12);
    /* Zero the sense buffer.  Some host adapters automatically request
     * sense on error.  0 is not a valid sense code.
     */
    memset ((void *) SCpnt->sense_buffer, 0, sizeof SCpnt->sense_buffer);
    SCpnt->request_buffer = buffer;
    SCpnt->request_bufflen = bufflen;
    SCpnt->old_use_sg = SCpnt->use_sg;
    if (SCpnt->cmd_len == 0)
	SCpnt->cmd_len = COMMAND_SIZE(SCpnt->cmnd[0]);
    SCpnt->old_cmd_len = SCpnt->cmd_len;

    /* Start the timer ticking.  */

    SCpnt->internal_timeout = NORMAL_TIMEOUT;
    SCpnt->abort_reason = 0;
    SCpnt->result = 0;

    if (mlqueue == 1 && host->hostt->use_new_eh_code){
	/* Assign a unique nonzero serial_number. */
	if (++serial_number == 0) serial_number = 1;
	SCpnt->serial_number = serial_number;
	scsi_mlqueue_insert(SCpnt, SCSI_MLQUEUE_HOST_BUSY);
    }
    else
	internal_cmnd (SCpnt);

    SCSI_LOG_MLQUEUE(3,printk ("Leaving scsi_do_cmd()\n"));
}

/* This function is the mid-level interrupt routine, which decides how
 *  to handle error conditions.  Each invocation of this function must
 *  do one and *only* one of the following:
 *
 *      1) Insert command in BH queue.
 *      2) Activate error handler for host.
 *
 * FIXME(eric) - I am concerned about stack overflow (still).  An interrupt could
 * come while we are processing the bottom queue, which would cause another command
 * to be stuffed onto the bottom queue, and it would in turn be processed as that
 * interrupt handler is returning.  Given a sufficiently steady rate of returning
 * commands, this could cause the stack to overflow.  I am not sure what is the most
 * appropriate solution here - we should probably keep a depth count, and not process
 * any commands while we still have a bottom handler active higher in the stack.
 *
 * There is currently code in the bottom half handler to monitor recursion in the bottom
 * handler and report if it ever happens.  If this becomes a problem, it won't be hard to
 * engineer something to deal with it so that only the outer layer ever does any real
 * processing.
 */
void
scsi_done (Scsi_Cmnd * SCpnt)
{

  /*
   * We don't have to worry about this one timing out any more.
   */
  scsi_delete_timer(SCpnt);

  /* Set the serial numbers back to zero */
  SCpnt->serial_number = 0;

  /*
   * First, see whether this command already timed out.  If so, we ignore
   * the response.  We treat it as if the command never finished.
   *
   * Since serial_number is now 0, the error handler cound detect this
   * situation and avoid to call the the low level driver abort routine.
   * (DB)
   */
  if( SCpnt->state == SCSI_STATE_TIMEOUT )
    {
      SCSI_LOG_MLCOMPLETE(1,printk("Ignoring completion of %p due to timeout status", SCpnt));
      return;
    }

  SCpnt->serial_number_at_timeout = 0;
  SCpnt->state = SCSI_STATE_BHQUEUE;
  SCpnt->owner = SCSI_OWNER_BH_HANDLER;
  SCpnt->bh_next = NULL;

  /*
   * Next, put this command in the BH queue.
   * 
   * We need a spinlock here, or compare and exchange if we can reorder incoming
   * Scsi_Cmnds, as it happens pretty often scsi_done is called multiple times
   * before bh is serviced. -jj
   *
   * We already have the io_request_lock here, since we are called from the
   * interrupt handler or the error handler. (DB)
   *
   */
  if (!scsi_bh_queue_head) {
  	scsi_bh_queue_head = SCpnt;
  	scsi_bh_queue_tail = SCpnt;
  } else {
  	scsi_bh_queue_tail->bh_next = SCpnt;
  	scsi_bh_queue_tail = SCpnt;
  }

  /*
   * Mark the bottom half handler to be run.
   */
  mark_bh(SCSI_BH);
}

/*
 * Procedure:   scsi_bottom_half_handler
 *
 * Purpose:     Called after we have finished processing interrupts, it
 *              performs post-interrupt handling for commands that may
 *              have completed.
 *
 * Notes:       This is called with all interrupts enabled.  This should reduce
 *              interrupt latency, stack depth, and reentrancy of the low-level
 *              drivers.
 *
 * The io_request_lock is required in all the routine. There was a subtle
 * race condition when scsi_done is called after a command has already
 * timed out but before the time out is processed by the error handler.
 * (DB)
 */
void scsi_bottom_half_handler(void)
{
  Scsi_Cmnd        * SCpnt;
  Scsi_Cmnd        * SCnext;
  unsigned long      flags;
  
  spin_lock_irqsave(&io_request_lock, flags);

  while(1==1)
  {
      SCpnt = scsi_bh_queue_head;