Edit report at https://bugs.php.net/bug.php?id=69044&edit=1
ID: 69044
User updated by: marc at gutt dot it
Reported by: marc at gutt dot it
Summary: time_sleep_until() starts to early
Status: Analyzed
Type: Bug
Package: Date/time related
Operating System: Debian
PHP Version: 5.4.37
Block user comment: N
Private report: N
New Comment:
Yes, date() seems to have a bug:
<?php
function udate($format, $timestamp=null) {
if (!isset($timestamp)) $timestamp = microtime();
// microtime(true)
if (count($t = explode(" ", $timestamp)) == 1) {
list($timestamp, $usec) = explode(".", $timestamp);
$usec = "." . $usec;
}
// microtime() is more precise
else {
$usec = $t[0];
$timestamp = $t[1];
}
// 7 decimal places for "u" is maximum
$usec = substr(sprintf('%.7f', $usec), 1);
$date = new DateTime(date('Y-m-d H:i:s' . $usec, $timestamp));
return $date->format($format);
}
echo "### first test ###\n";
$sleep_until = round(microtime(true)) + 3.002;
echo "sleep: " . udate("Y-m-d\TH:i:s.u", $sleep_until) . "\n";
time_sleep_until($sleep_until);
echo "udate: " . udate("Y-m-d\TH:i:s.u", microtime(true)) . "\n";
echo "date : " . date("Y-m-d\TH:i:s") . "\n";
echo "### second test ###\n";
$sleep_until = round(microtime(true)) + 3.003;
echo "sleep: " . udate("Y-m-d\TH:i:s.u", $sleep_until) . "\n";
time_sleep_until($sleep_until);
echo "udate: " . udate("Y-m-d\TH:i:s.u", microtime(true)) . "\n";
echo "date : " . date("Y-m-d\TH:i:s") . "\n";
/* results:
### first test ###
sleep: 2015-02-14T14:29:51.002000
udate: 2015-02-14T14:29:51.002100
date : 2015-02-14T14:29:50
### second test ###
sleep: 2015-02-14T14:29:54.003000
udate: 2015-02-14T14:29:54.003100
date : 2015-02-14T14:29:54
*/
?>
Previous Comments:
------------------------------------------------------------------------
[2015-02-14 02:00:02] requinix@php.net
By the way, the code works fine on Windows: time() - $sleep_until = 0 consistently. Tried the same
code on Ubuntu 14.04 and would get -1 consistently.
------------------------------------------------------------------------
[2015-02-14 01:44:44] yohgaki@php.net
You can see it's sleeping as it supposed by replacing date() to microtime()
<?php
$sleep_until = microtime(true) + 1;
echo "sleep until " . $sleep_until ."\n";
time_sleep_until($sleep_until);
echo "woke up at " . microtime(true);
?>
------------------------------------------------------------------------
[2015-02-14 01:39:34] yohgaki@php.net
My previous analysis is wrong.
time_sleep_until() sleeps as it supposed. It seems date() is doing something wrong.
------------------------------------------------------------------------
[2015-02-14 00:47:54] yohgaki@php.net
Oops. Round margin should be something like 0.99. Or use ceil() to be precise.
------------------------------------------------------------------------
[2015-02-14 00:45:32] yohgaki@php.net
The cause of this is floating point calculation. It's rounded.
Possible patch is
diff --git a/ext/standard/basic_functions.c b/ext/standard/basic_functions.c
index 2b70414..44a41e4 100644
--- a/ext/standard/basic_functions.c
+++ b/ext/standard/basic_functions.c
@@ -4486,8 +4486,8 @@ PHP_FUNCTION(time_sleep_until)
if (php_req.tv_sec > c_ts) { /* rounding up occurred */
php_req.tv_sec--;
}
- /* 1sec = 1000000000 nanoseconds */
- php_req.tv_nsec = (long) ((c_ts - php_req.tv_sec) * 1000000000.00);
+ /* 1sec = 1000000000 nanoseconds. Add 0.5 sec round margin */
+ php_req.tv_nsec = (long) ((c_ts - php_req.tv_sec) * 1000000000.00 + 0.5) ;
while (nanosleep(&php_req, &php_rem)) {
if (errno == EINTR) {
------------------------------------------------------------------------
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