mariadb/mysys/my_lock.c

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library 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
   Library General Public License for more details.
   
   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
   MA 02111-1307, USA */

#include "mysys_priv.h"
#include "mysys_err.h"
#include <errno.h>
#undef MY_HOW_OFTEN_TO_ALARM
#define MY_HOW_OFTEN_TO_ALARM ((int) my_time_to_wait_for_lock)
#ifdef NO_ALARM_LOOP
#undef NO_ALARM_LOOP
#endif
#include <my_alarm.h>
#ifdef __WIN__
#include <sys/locking.h>
#endif
#ifdef __EMX__
#define INCL_BASE
#define INCL_NOPMAPI
#include <os2emx.h>
#endif

	/* Lock a part of a file */

int my_lock(File fd, int locktype, my_off_t start, my_off_t length,
	    myf MyFlags)
{
#ifdef HAVE_FCNTL
  int value;
  ALARM_VARIABLES;
#endif
  DBUG_ENTER("my_lock");
  DBUG_PRINT("my",("Fd: %d  Op: %d  start: %ld  Length: %ld  MyFlags: %d",
		   fd,locktype,(long) start,(long) length,MyFlags));
#ifdef VMS
  DBUG_RETURN(0);
#else
  if (my_disable_locking)
    DBUG_RETURN(0);

#if defined(__EMX__) || defined(OS2)

   if (!_lock64( fd, locktype, start, length, MyFlags))
    DBUG_RETURN(0);

#elif defined(HAVE_LOCKING)
  /* Windows */
  {
    my_bool error;
    pthread_mutex_lock(&my_file_info[fd].mutex);
    if (MyFlags & MY_SEEK_NOT_DONE)
      VOID(my_seek(fd,start,MY_SEEK_SET,MYF(MyFlags & ~MY_SEEK_NOT_DONE)));
    error= locking(fd,locktype,(ulong) length) && errno != EINVAL;
    pthread_mutex_unlock(&my_file_info[fd].mutex);
    if (!error)
      DBUG_RETURN(0);
  }
#else
#if defined(HAVE_FCNTL)
  {
    struct flock lock;
    lock.l_type= (short) locktype;
    lock.l_whence=0L;
    lock.l_start=(long) start;
    lock.l_len=(long) length;
    if (MyFlags & MY_DONT_WAIT)
    {
      if (fcntl(fd,F_SETLK,&lock) != -1)	/* Check if we can lock */
	DBUG_RETURN(0);			/* Ok, file locked */
      DBUG_PRINT("info",("Was locked, trying with alarm"));
      ALARM_INIT;
      while ((value=fcntl(fd,F_SETLKW,&lock)) && ! ALARM_TEST &&
	     errno == EINTR)
      {			/* Setup again so we don`t miss it */
	ALARM_REINIT;
      }
      ALARM_END;
      if (value != -1)
	DBUG_RETURN(0);
      if (errno == EINTR)
	errno=EAGAIN;
    }
    else if (fcntl(fd,F_SETLKW,&lock) != -1) /* Wait until a lock */
      DBUG_RETURN(0);
  }
#else
  if (MyFlags & MY_SEEK_NOT_DONE)
    VOID(my_seek(fd,start,MY_SEEK_SET,MYF(MyFlags & ~MY_SEEK_NOT_DONE)));
  if (lockf(fd,locktype,length) != -1)
    DBUG_RETURN(0);
#endif /* HAVE_FCNTL */
#endif /* HAVE_LOCKING */

	/* We got an error. We don't want EACCES errors */
  my_errno=(errno == EACCES) ? EAGAIN : errno ? errno : -1;
  if (MyFlags & MY_WME)
  {
    if (locktype == F_UNLCK)
      my_error(EE_CANTUNLOCK,MYF(ME_BELL+ME_WAITTANG),my_errno);
    else
      my_error(EE_CANTLOCK,MYF(ME_BELL+ME_WAITTANG),my_errno);
  }
  DBUG_PRINT("error",("my_errno: %d (%d)",my_errno,errno));
  DBUG_RETURN(-1);
#endif	/* ! VMS */
} /* my_lock */