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BUG: Timezone failures with threads under Cygwin 1.5.25
- From: "Jerry D. Hedden" <jdhedden at cpan dot org>
- To: cygwin at cygwin dot com
- Cc: pp <perl5-porters at perl dot org>
- Date: Mon, 10 Dec 2007 17:00:52 -0500
- Subject: BUG: Timezone failures with threads under Cygwin 1.5.25
(CC'ed to perl5-porters for reference.)
The Perl test suite contains a file
(perl-current/ext/threads/t/libc.t) that exercises the
'localtime' call under threads. Here's the main code:
my $i = 10;
my $y = 20000;
my %localtime;
for (1..$i) {
$localtime{$_} = localtime($_);
};
my @threads;
for (1..$i) {
$threads[$_] = threads->create(sub {
my $arg = shift;
my $localtime = $localtime{$arg};
my $error = 0;
for (1..$y) {
my $lt = localtime($arg);
if ($localtime ne $lt) {
$error++;
}
}
return $error;
}, $_);
}
for (1..$i) {
is($threads[$_]->join(), 0, 'localtime() thread-safe');
}
This runs 10 threads that call 'localtime' 20,000 times
each.
Under 1.5.24, this test always passes. Under 1.5.25, it is
now frequently failing. If I add a debugging call in the
central most loop:
print("got: $lt exp: $localtime\n");
I get the following as typical of the problem:
5 perl-current > ./perl -Ilib ext/threads/t/libc.t
1..11
ok 1 - use threads
got: Wed Dec 31 20:00:08 1969 exp: Wed Dec 31 19:00:08 1969
got: Wed Dec 31 20:00:07 1969 exp: Wed Dec 31 19:00:07 1969
got: Wed Dec 31 20:00:06 1969 exp: Wed Dec 31 19:00:06 1969
got: Wed Dec 31 20:00:08 1969 exp: Wed Dec 31 19:00:08 1969
got: Wed Dec 31 20:00:07 1969 exp: Wed Dec 31 19:00:07 1969
got: Wed Dec 31 20:00:06 1969 exp: Wed Dec 31 19:00:06 1969
got: Wed Dec 31 20:00:10 1969 exp: Wed Dec 31 19:00:10 1969
ok 2 - localtime() thread-safe
ok 3 - localtime() thread-safe
ok 4 - localtime() thread-safe
ok 5 - localtime() thread-safe
ok 6 - localtime() thread-safe
not ok 7 - localtime() thread-safe
# Failed at ext/threads/t/libc.t line 52
# got '2'
# expected '0'
not ok 8 - localtime() thread-safe
# Failed at ext/threads/t/libc.t line 52
# got '2'
# expected '0'
not ok 9 - localtime() thread-safe
# Failed at ext/threads/t/libc.t line 52
# got '2'
# expected '0'
ok 10 - localtime() thread-safe
not ok 11 - localtime() thread-safe
# Failed at ext/threads/t/libc.t line 52
# got '1'
# expected '0'
This shows a 1 hour difference between the expected and
actual results - which looks like a timezone issue.
As the changes for 1.5.25 include numerous references to
timezone handling changes, I suspect there may be some
re-entrancy bug in those changes.
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