1: # include   "../ingres.h"
   2: # include   "../tree.h"
   3: # include   "decomp.h"
   4: # include   "../lock.h"
   5: /*
   6: **	lockit - sets relation locks for integrity locking
   7: **
   8: **	arguements:
   9: **		root- the root of a query tree;
  10: **		resvar- index of variable to be updated.
  11: **
  12: */
  13: lockit(root, resvar)
  14: struct querytree    *root;
  15: int         resvar;
  16: {
  17:     register struct querytree   *r;
  18:     register int            i, j;
  19:     long                vlist[MAXRANGE];
  20:     int             bmap, cv;
  21:     char                mode;
  22:     int             skvr;
  23:     int             redo;
  24:     struct descriptor       *d, *openr1();
  25:     long                restid;
  26:     int             k;
  27: 
  28:     r = root;
  29:     bmap = ((struct qt_root *)r)->lvarm | ((struct qt_root *)r)->rvarm;
  30:     if (resvar >= 0)
  31:         bmap |= 01 << resvar;
  32:     else
  33:         restid = -1;
  34:     i = 0;
  35:     /* put relids of relations to be locked into vlist
  36: 	   check for and remove duplicates */
  37:     for (j = 0; j < MAXRANGE; j++)
  38:         if (bmap & (01 << j))
  39:         {
  40:             d = openr1(j);
  41:             if (j == resvar)
  42:                 restid = d->reltid;
  43:             for (k = 0; k < i; k++)
  44:                 if (vlist[k] == d->reltid)
  45:                     break;
  46:             if (k == i)
  47:                 vlist[i++] = d->reltid;
  48:         }
  49:     cv = i;
  50: /*
  51:  *	set the locks: set the first lock with the sleep option
  52:  *			set other locks checking for failure;
  53:  *			if failure, release all locks, sleep on blocking
  54:  *			lock.
  55:  */
  56:     skvr = -1;
  57:     do
  58:     {
  59:         /* skvr is the index of the relation already locked
  60: 		   try to lock the remaining relations */
  61:         redo = FALSE;
  62:         for (i = 0; i < cv; i++)
  63:             if (i != skvr)
  64:             {
  65:                 if (restid == vlist[i])
  66:                     mode = M_EXCL;
  67:                 else
  68:                     mode = M_SHARE;
  69:                 if (setrll(A_RTN, vlist[i], mode) < 0)
  70:                     /* a lock request failed */
  71:                 {
  72:                     unlall();   /* release all locks */
  73:                     setrll(A_SLP, vlist[i], mode);
  74:                             /* wait on problem lock*/
  75:                     skvr = i;
  76:                     redo = TRUE;
  77:                     break;  /* reset the other locks */
  78:                 }
  79:             }
  80:     }
  81:     while (redo);
  82: }

Defined functions

lockit defined in line 13; used 1 times
Last modified: 1995-04-14
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