path: root/source3/smbd/blocking.c

/* 
   Unix SMB/CIFS implementation.
   Blocking Locking functions
   Copyright (C) Jeremy Allison 1998-2003
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

extern char *OutBuffer;

/****************************************************************************
 This is the structure to queue to implement blocking locks.
 notify. It consists of the requesting SMB and the expiry time.
*****************************************************************************/

typedef struct {
  ubi_slNode msg_next;
  int com_type;
  files_struct *fsp;
  time_t expire_time;
  int lock_num;
  SMB_BIG_UINT offset;
  SMB_BIG_UINT count;
  uint16 lock_pid;
  char *inbuf;
  int length;
} blocking_lock_record;

static ubi_slList blocking_lock_queue = { NULL, (ubi_slNodePtr)&blocking_lock_queue, 0};

/****************************************************************************
 Destructor for the above structure.
****************************************************************************/

static void free_blocking_lock_record(blocking_lock_record *blr)
{
  SAFE_FREE(blr->inbuf);
  SAFE_FREE(blr);
}

/****************************************************************************
 Get the files_struct given a particular queued SMB.
*****************************************************************************/

static files_struct *get_fsp_from_pkt(char *inbuf)
{
  switch(CVAL(inbuf,smb_com)) {
  case SMBlock:
  case SMBlockread:
    return file_fsp(inbuf,smb_vwv0);
  case SMBlockingX:
    return file_fsp(inbuf,smb_vwv2);
  default:
    DEBUG(0,("get_fsp_from_pkt: PANIC - unknown type on blocking lock queue - exiting.!\n"));
    exit_server("PANIC - unknown type on blocking lock queue");
  }
  return NULL; /* Keep compiler happy. */
}

/****************************************************************************
 Determine if this is a secondary element of a chained SMB.
  **************************************************************************/

static BOOL in_chained_smb(void)
{
  return (chain_size != 0);
}

static void received_unlock_msg(int msg_type, pid_t src, void *buf, size_t len);

/****************************************************************************
 Function to push a blocking lock request onto the lock queue.
****************************************************************************/

BOOL push_blocking_lock_request( char *inbuf, int length, int lock_timeout,
		int lock_num, uint16 lock_pid, SMB_BIG_UINT offset, SMB_BIG_UINT count)
{
  static BOOL set_lock_msg;
  blocking_lock_record *blr;
  NTSTATUS status;

  if(in_chained_smb() ) {
    DEBUG(0,("push_blocking_lock_request: cannot queue a chained request (currently).\n"));
    return False;
  }

  /*
   * Now queue an entry on the blocking lock queue. We setup
   * the expiration time here.
   */

  if((blr = (blocking_lock_record *)malloc(sizeof(blocking_lock_record))) == NULL) {
    DEBUG(0,("push_blocking_lock_request: Malloc fail !\n" ));
    return False;
  }

  if((blr->inbuf = (char *)malloc(length)) == NULL) {
    DEBUG(0,("push_blocking_lock_request: Malloc fail (2)!\n" ));
    SAFE_FREE(blr);
    return False;
  }

  blr->com_type = CVAL(inbuf,smb_com);
  blr->fsp = get_fsp_from_pkt(inbuf);
  blr->expire_time = (lock_timeout == -1) ? (time_t)-1 : time(NULL) + (time_t)lock_timeout;
  blr->lock_num = lock_num;
  blr->lock_pid = lock_pid;
  blr->offset = offset;
  blr->count = count;
  memcpy(blr->inbuf, inbuf, length);
  blr->length = length;

  /* Add a pending lock record for this. */
  status = brl_lock(blr->fsp->dev, blr->fsp->inode, blr->fsp->fnum,
		lock_pid, sys_getpid(), blr->fsp->conn->cnum,
		offset, count,
		PENDING_LOCK);

  if (!NT_STATUS_IS_OK(status)) {
	DEBUG(0,("push_blocking_lock_request: failed to add PENDING_LOCK record.\n"));
	free_blocking_lock_record(blr);
	return False;
  }

  ubi_slAddTail(&blocking_lock_queue, blr);

  /* Ensure we'll receive messages when this is unlocked. */
  if (!set_lock_msg) {
	  message_register(MSG_SMB_UNLOCK, received_unlock_msg);
	  set_lock_msg = True;
  }

  DEBUG(3,("push_blocking_lock_request: lock request length=%d blocked with expiry time %d (+%d) \
for fnum = %d, name = %s\n", length, (int)blr->expire_time, lock_timeout,
        blr->fsp->fnum, blr->fsp->fsp_name ));

  return True;
}

/****************************************************************************
 Return a smd with a given size.
*****************************************************************************/

static void send_blocking_reply(char *outbuf, int outsize)
{
	if(outsize > 4)
		smb_setlen(outbuf,outsize - 4);

	if (!send_smb(smbd_server_fd(),outbuf))
		exit_server("send_blocking_reply: send_smb failed.");
}

/****************************************************************************
 Return a lockingX success SMB.
*****************************************************************************/

static void reply_lockingX_success(blocking_lock_record *blr)
{
  char *outbuf = OutBuffer;
  int bufsize = BUFFER_SIZE;
  char *inbuf = blr->inbuf;
  int outsize = 0;

  construct_reply_common(inbuf, outbuf);
  set_message(outbuf,2,0,True);

  /*
   * As this message is a lockingX call we must handle
   * any following chained message correctly.
   * This is normally handled in construct_reply(),
   * but as that calls switch_message, we can't use
   * that here and must set up the chain info manually.
   */

  outsize = chain_reply(inbuf,outbuf,blr->length,bufsize);

  outsize += chain_size;

  send_blocking_reply(outbuf,outsize);
}

/****************************************************************************
 Return a generic lock fail error blocking call.
*****************************************************************************/

static void generic_blocking_lock_error(blocking_lock_record *blr, NTSTATUS status)
{
	char *outbuf = OutBuffer;
	char *inbuf = blr->inbuf;
	construct_reply_common(inbuf, outbuf);

	/* whenever a timeout is given w2k maps LOCK_NOT_GRANTED to
	   FILE_LOCK_CONFLICT! (tridge) */
	if (NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
		status = NT_STATUS_FILE_LOCK_CONFLICT;
	}

	ERROR_NT(status);
	if (!send_smb(smbd_server_fd(),outbuf))
		exit_server("generic_blocking_lock_error: send_smb failed.");
}

/****************************************************************************
 Return a lock fail error for a lockingX call. Undo all the locks we have 
 obtained first.
*****************************************************************************/

static void reply_lockingX_error(blocking_lock_record *blr, NTSTATUS status)
{
	char *inbuf = blr->inbuf;
	files_struct *fsp = blr->fsp;
	connection_struct *conn = conn_find(SVAL(inbuf,smb_tid));
	uint16 num_ulocks = SVAL(inbuf,smb_vwv6);
	SMB_BIG_UINT count = (SMB_BIG_UINT)0, offset = (SMB_BIG_UINT) 0;
	uint16 lock_pid;
	unsigned char locktype = CVAL(inbuf,smb_vwv3);
	BOOL large_file_format = (locktype & LOCKING_ANDX_LARGE_FILES);
	char *data;
	int i;

	data = smb_buf(inbuf) + ((large_file_format ? 20 : 10)*num_ulocks);
	
	/* 
	 * Data now points at the beginning of the list
	 * of smb_lkrng structs.
	 */

	/*
	 * Ensure we don't do a remove on the lock that just failed,
	 * as under POSIX rules, if we have a lock already there, we
	 * will delete it (and we shouldn't) .....
	 */
	
	for(i = blr->lock_num - 1; i >= 0; i--) {
		BOOL err;
		
		lock_pid = get_lock_pid( data, i, large_file_format);
		count = get_lock_count( data, i, large_file_format);
		offset = get_lock_offset( data, i, large_file_format, &err);
		
		/*
		 * We know err cannot be set as if it was the lock
		 * request would never have been queued. JRA.
		 */
		
		do_unlock(fsp,conn,lock_pid,count,offset);
	}
	
	generic_blocking_lock_error(blr, status);
}

/****************************************************************************
 Return a lock fail error.
*****************************************************************************/

static void blocking_lock_reply_error(blocking_lock_record *blr, NTSTATUS status)
{
	switch(blr->com_type) {
	case SMBlock:
	case SMBlockread:
		generic_blocking_lock_error(blr, status);
		break;
	case SMBlockingX:
		reply_lockingX_error(blr, status);
		break;
	default:
		DEBUG(0,("blocking_lock_reply_error: PANIC - unknown type on blocking lock queue - exiting.!\n"));
		exit_server("PANIC - unknown type on blocking lock queue");
	}
}

/****************************************************************************
 Attempt to finish off getting all pending blocking locks for a lockread call.
 Returns True if we want to be removed from the list.
*****************************************************************************/

static BOOL process_lockread(blocking_lock_record *blr)
{
	char *outbuf = OutBuffer;
	char *inbuf = blr->inbuf;
	ssize_t nread = -1;
	char *data, *p;
	int outsize = 0;
	SMB_BIG_UINT startpos;
	size_t numtoread;
	NTSTATUS status;
	connection_struct *conn = conn_find(SVAL(inbuf,smb_tid));
	files_struct *fsp = blr->fsp;

	numtoread = SVAL(inbuf,smb_vwv1);
	startpos = (SMB_BIG_UINT)IVAL(inbuf,smb_vwv2);
	
	numtoread = MIN(BUFFER_SIZE-outsize,numtoread);
	data = smb_buf(outbuf) + 3;
 
	status = do_lock_spin( fsp, conn, SVAL(inbuf,smb_pid), (SMB_BIG_UINT)numtoread, 
			  startpos, READ_LOCK);
	if (NT_STATUS_V(status)) {
		if (!NT_STATUS_EQUAL(status,NT_STATUS_LOCK_NOT_GRANTED) &&
			!NT_STATUS_EQUAL(status,NT_STATUS_FILE_LOCK_CONFLICT)) {
			/*
			 * We have other than a "can't get lock"
			 * error. Send an error.
			 * Return True so we get dequeued.
			 */
			generic_blocking_lock_error(blr, status);
			return True;
		}

		/*
		 * Still waiting for lock....
		 */
		
		DEBUG(10,("process_lockread: failed to get lock for file = %s. Still waiting....\n",
			  fsp->fsp_name));
		return False;
	}

	nread = read_file(fsp,data,startpos,numtoread);

	if (nread < 0) {
		generic_blocking_lock_error(blr,NT_STATUS_ACCESS_DENIED);
		return True;
	}
	
	construct_reply_common(inbuf, outbuf);
	outsize = set_message(outbuf,5,0,True);
	
	outsize += nread;
	SSVAL(outbuf,smb_vwv0,nread);
	SSVAL(outbuf,smb_vwv5,nread+3);
	p = smb_buf(outbuf);
	*p++ = 1;
	SSVAL(p,0,nread); p += 2;
	set_message_end(outbuf, p+nread);
	
	DEBUG(3, ( "process_lockread file = %s, fnum=%d num=%d nread=%d\n",
		   fsp->fsp_name, fsp->fnum, (int)numtoread, (int)nread ) );
	
	send_blocking_reply(outbuf,outsize);
	return True;
}

/****************************************************************************
 Attempt to finish off getting all pending blocking locks for a lock call.
 Returns True if we want to be removed from the list.
*****************************************************************************/

static BOOL process_lock(blocking_lock_record *blr)
{
	char *outbuf = OutBuffer;
	char *inbuf = blr->inbuf;
	int outsize;
	SMB_BIG_UINT count = (SMB_BIG_UINT)0, offset = (SMB_BIG_UINT)0;
	NTSTATUS status;
	connection_struct *conn = conn_find(SVAL(inbuf,smb_tid));
	files_struct *fsp = blr->fsp;

	count = IVAL_TO_SMB_OFF_T(inbuf,smb_vwv1);
	offset = IVAL_TO_SMB_OFF_T(inbuf,smb_vwv3);

	errno = 0;
	status = do_lock_spin(fsp, conn, SVAL(inbuf,smb_pid), count, 
			 offset, WRITE_LOCK);
	if (NT_STATUS_IS_ERR(status)) {
		if (!NT_STATUS_EQUAL(status,NT_STATUS_LOCK_NOT_GRANTED) &&
			!NT_STATUS_EQUAL(status,NT_STATUS_FILE_LOCK_CONFLICT)) {
			/*
			 * We have other than a "can't get lock"
			 * error. Send an error.
			 * Return True so we get dequeued.
			 */
			
			blocking_lock_reply_error(blr, status);
			return True;
		}
		/*
		 * Still can't get the lock - keep waiting.
		 */
		DEBUG(10,("process_lock: failed to get lock for file = %s. Still waiting....\n",
			  fsp->fsp_name));
		return False;
	}

	/*
	 * Success - we got the lock.
	 */
	
	DEBUG(3,("process_lock : file=%s fnum=%d offset=%.0f count=%.0f\n",
		 fsp->fsp_name, fsp->fnum, (double)offset, (double)count));
	
	construct_reply_common(inbuf, outbuf);
	outsize = set_message(outbuf,0,0,True);
	send_blocking_reply(outbuf,outsize);
	return True;
}

/****************************************************************************
 Attempt to finish off getting all pending blocking locks for a lockingX call.
 Returns True if we want to be removed from the list.
*****************************************************************************/

static BOOL process_lockingX(blocking_lock_record *blr)
{
	char *inbuf = blr->inbuf;
	unsigned char locktype = CVAL(inbuf,smb_vwv3);
	files_struct *fsp = blr->fsp;
	connection_struct *conn = conn_find(SVAL(inbuf,smb_tid));
	uint16 num_ulocks = SVAL(inbuf,smb_vwv6);
	uint16 num_locks = SVAL(inbuf,smb_vwv7);
	SMB_BIG_UINT count = (SMB_BIG_UINT)0, offset = (SMB_BIG_UINT)0;
	uint16 lock_pid;
	BOOL large_file_format = (locktype & LOCKING_ANDX_LARGE_FILES);
	char *data;
	NTSTATUS status = NT_STATUS_OK;

	data = smb_buf(inbuf) + ((large_file_format ? 20 : 10)*num_ulocks);

	/* 
	 * Data now points at the beginning of the list
	 * of smb_lkrng structs.
	 */
	
	for(; blr->lock_num < num_locks; blr->lock_num++) {
		BOOL err;

		lock_pid = get_lock_pid( data, blr->lock_num, large_file_format);
		count = get_lock_count( data, blr->lock_num, large_file_format);
		offset = get_lock_offset( data, blr->lock_num, large_file_format, &err);
		
		/*
		 * We know err cannot be set as if it was the lock
		 * request would never have been queued. JRA.
		 */
		errno = 0;
		status = do_lock_spin(fsp,conn,lock_pid,count,offset, 
				 ((locktype & 1) ? READ_LOCK : WRITE_LOCK));
		if (NT_STATUS_IS_ERR(status)) break;
	}

	if(blr->lock_num == num_locks) {
		/*
		 * Success - we got all the locks.
		 */
		
		DEBUG(3,("process_lockingX file = %s, fnum=%d type=%d num_locks=%d\n",
			 fsp->fsp_name, fsp->fnum, (unsigned int)locktype, num_locks) );

		reply_lockingX_success(blr);
		return True;
	} else if (!NT_STATUS_EQUAL(status,NT_STATUS_LOCK_NOT_GRANTED) &&
			!NT_STATUS_EQUAL(status,NT_STATUS_FILE_LOCK_CONFLICT)) {
			/*
			 * We have other than a "can't get lock"
			 * error. Free any locks we had and return an error.
			 * Return True so we get dequeued.
			 */
		
		blocking_lock_reply_error(blr, status);
		return True;
	}

	/*
	 * Still can't get all the locks - keep waiting.
	 */
	
	DEBUG(10,("process_lockingX: only got %d locks of %d needed for file %s, fnum = %d. \
Waiting....\n", 
		  blr->lock_num, num_locks, fsp->fsp_name, fsp->fnum));
	
	return False;
}

/****************************************************************************
 Process a blocking lock SMB.
 Returns True if we want to be removed from the list.
*****************************************************************************/

static BOOL blocking_lock_record_process(blocking_lock_record *blr)
{
  switch(blr->com_type) {
  case SMBlock:
    return process_lock(blr);
  case SMBlockread:
    return process_lockread(blr);
  case SMBlockingX:
    return process_lockingX(blr);
  default:
    DEBUG(0,("blocking_lock_record_process: PANIC - unknown type on blocking lock queue - exiting.!\n"));
    exit_server("PANIC - unknown type on blocking lock queue");
  }
  return False; /* Keep compiler happy. */
}

/****************************************************************************
 Delete entries by fnum from the blocking lock pending queue.
*****************************************************************************/

void remove_pending_lock_requests_by_fid(files_struct *fsp)
{
  blocking_lock_record *blr = (blocking_lock_record *)ubi_slFirst( &blocking_lock_queue );
  blocking_lock_record *prev = NULL;

  while(blr != NULL) {
    if(blr->fsp->fnum == fsp->fnum) {

      DEBUG(10,("remove_pending_lock_requests_by_fid - removing request type %d for \
file %s fnum = %d\n", blr->com_type, fsp->fsp_name, fsp->fnum ));

      brl_unlock(blr->fsp->dev, blr->fsp->inode, blr->fsp->fnum,
		blr->lock_pid, sys_getpid(), blr->fsp->conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);

      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      continue;
    }

    prev = blr;
    blr = (blocking_lock_record *)ubi_slNext(blr);
  }
}

/****************************************************************************
 Delete entries by mid from the blocking lock pending queue. Always send reply.
*****************************************************************************/

void remove_pending_lock_requests_by_mid(int mid)
{
  blocking_lock_record *blr = (blocking_lock_record *)ubi_slFirst( &blocking_lock_queue );
  blocking_lock_record *prev = NULL;

  while(blr != NULL) {
    if(SVAL(blr->inbuf,smb_mid) == mid) {
      files_struct *fsp = blr->fsp;

      DEBUG(10,("remove_pending_lock_requests_by_mid - removing request type %d for \
file %s fnum = %d\n", blr->com_type, fsp->fsp_name, fsp->fnum ));

      blocking_lock_reply_error(blr,NT_STATUS_CANCELLED);
      brl_unlock(blr->fsp->dev, blr->fsp->inode, blr->fsp->fnum,
		blr->lock_pid, sys_getpid(), blr->fsp->conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);
      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      continue;
    }

    prev = blr;
    blr = (blocking_lock_record *)ubi_slNext(blr);
  }
}

/****************************************************************************
  Set a flag as an unlock request affects one of our pending locks.
*****************************************************************************/

static void received_unlock_msg(int msg_type, pid_t src, void *buf, size_t len)
{
	DEBUG(10,("received_unlock_msg\n"));
	process_blocking_lock_queue(time(NULL));
}

/****************************************************************************
 Return the number of seconds to the next blocking locks timeout, or default_timeout
*****************************************************************************/

unsigned blocking_locks_timeout(unsigned default_timeout)
{
	unsigned timeout = default_timeout;
	time_t t;
	blocking_lock_record *blr = (blocking_lock_record *)ubi_slFirst(&blocking_lock_queue);

	/* note that we avoid the time() syscall if there are no blocking locks */
	if (!blr)
		return timeout;

	t = time(NULL);

	while (blr) {
		if ((blr->expire_time != (time_t)-1) &&
					(timeout > (blr->expire_time - t))) {
			timeout = blr->expire_time - t;
		}
		blr = (blocking_lock_record *)ubi_slNext(blr);
	}

	if (timeout < 1)
		timeout = 1;

	return timeout;
}

/****************************************************************************
 Process the blocking lock queue. Note that this is only called as root.
*****************************************************************************/

void process_blocking_lock_queue(time_t t)
{
  blocking_lock_record *blr = (blocking_lock_record *)ubi_slFirst( &blocking_lock_queue );
  blocking_lock_record *prev = NULL;

  if(blr == NULL)
    return;

  /*
   * Go through the queue and see if we can get any of the locks.
   */

  while(blr != NULL) {
    connection_struct *conn = NULL;
    uint16 vuid;
    files_struct *fsp = NULL;

    /*
     * Ensure we don't have any old chain_fsp values
     * sitting around....
     */
    chain_size = 0;
    file_chain_reset();
    fsp = blr->fsp;

    conn = conn_find(SVAL(blr->inbuf,smb_tid));
    vuid = (lp_security() == SEC_SHARE) ? UID_FIELD_INVALID :
                  SVAL(blr->inbuf,smb_uid);

    DEBUG(5,("process_blocking_lock_queue: examining pending lock fnum = %d for file %s\n",
          fsp->fnum, fsp->fsp_name ));

    if((blr->expire_time != -1) && (blr->expire_time <= t)) {
      /*
       * Lock expired - throw away all previously
       * obtained locks and return lock error.
       */
      DEBUG(5,("process_blocking_lock_queue: pending lock fnum = %d for file %s timed out.\n",
          fsp->fnum, fsp->fsp_name ));

      brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
		blr->lock_pid, sys_getpid(), conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);

      blocking_lock_reply_error(blr,NT_STATUS_FILE_LOCK_CONFLICT);
      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      continue;
    }

    if(!change_to_user(conn,vuid)) {
      DEBUG(0,("process_blocking_lock_queue: Unable to become user vuid=%d.\n",
            vuid ));
      /*
       * Remove the entry and return an error to the client.
       */
      blocking_lock_reply_error(blr,NT_STATUS_ACCESS_DENIED);

      brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
		blr->lock_pid, sys_getpid(), conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);

      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      continue;
    }

    if(!set_current_service(conn,True)) {
      DEBUG(0,("process_blocking_lock_queue: Unable to become service Error was %s.\n", strerror(errno) ));
      /*
       * Remove the entry and return an error to the client.
       */
      blocking_lock_reply_error(blr,NT_STATUS_ACCESS_DENIED);

      brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
		blr->lock_pid, sys_getpid(), conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);

      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      change_to_root_user();
      continue;
    }

    /*
     * Go through the remaining locks and try and obtain them.
     * The call returns True if all locks were obtained successfully
     * and False if we still need to wait.
     */

    if(blocking_lock_record_process(blr)) {

      brl_unlock(fsp->dev, fsp->inode, fsp->fnum,
		blr->lock_pid, sys_getpid(), conn->cnum,
		blr->offset, blr->count, True, NULL, NULL);

      free_blocking_lock_record((blocking_lock_record *)ubi_slRemNext( &blocking_lock_queue, prev));
      blr = (blocking_lock_record *)(prev ? ubi_slNext(prev) : ubi_slFirst(&blocking_lock_queue));
      change_to_root_user();
      continue;
    }

    change_to_root_user();

    /*
     * Move to the next in the list.
     */
    prev = blr;
    blr = (blocking_lock_record *)ubi_slNext(blr);
  }
}