include/lock.php

   1 <?php
   2
   3 // Provide some ability to lock a PHP function so that multiple processes
   4 // can't run the function concurrently
   5 if(! function_exists('lock_function')) {
   6 function lock_function($fn_name, $block = true, $wait_sec = 2) {
   7         if( $wait_sec == 0 )
   8                 $wait_sec = 2;  // don't let the user pick a value that's likely to crash the system
   9
  10         $got_lock = false;
  11
  12         do {
  13                 q("LOCK TABLE lock WRITE");
  14                 $r = q("SELECT locked FROM lock WHERE name = '%s' LIMIT 1",
  15                         dbesc($fn_name)
  16                 );
  17
  18                 if((count($r)) && (! $r[0]['locked'])) {
  19                         q("UPDATE lock SET locked = 1 WHERE name = '%s' LIMIT 1",
  20                                 dbesc($fn_name)
  21                         );
  22                         $got_lock = true;
  23                 }
  24                 elseif(! $r) { // the Boolean value for count($r) should be equivalent to the Boolean value of $r
  25                         q("INSERT INTO lock ( name, locked ) VALUES ( '%s', 1 )",
  26                                 dbesc($fn_name)
  27                         );
  28                         $got_lock = true;
  29                 }
  30
  31                 q("UNLOCK TABLES");
  32
  33                 if(($block) && (! $got_lock))
  34                         sleep($wait_sec);
  35
  36         } while(($block) && (! $got_lock));
  37
  38         logger('lock_function: function ' . $fn_name . ' with blocking = ' . $block . ' got_lock = ' . $got_lock, LOGGER_DEBUG);
  39
  40         return $got_lock;
  41 }}
  42
  43
  44 if(! function_exists('block_on_function_lock')) {
  45 function block_on_function_lock($fn_name, $wait_sec = 2) {
  46         if( $wait_sec == 0 )
  47                 $wait_sec = 2;  // don't let the user pick a value that's likely to crash the system
  48
  49         do {
  50                 $r = q("SELECT locked FROM lock WHERE name = '%s' LIMIT 1",
  51                                 dbesc(fn_name)
  52                      );
  53
  54                 if(count($r) && $r[0]['locked'])
  55                         sleep($wait_sec);
  56
  57         } while(count($r) && $r[0]['locked']);
  58
  59         return;
  60 }}
  61
  62
  63 if(! function_exists('unlock_function')) {
  64 function unlock_function(fn_name) {
  65         //$r = q("LOCK TABLE lock WRITE");
  66         $r = q("UPDATE lock SET locked = 0 WHERE name = '%s' LIMIT 1",
  67                         dbesc(fn_name)
  68              );
  69         //$r = q("UNLOCK TABLES");
  70
  71         logger('unlock_function: released lock for function ' . fn_name, LOGGER_DEBUG);
  72
  73         return;
  74 }}