Can I use lock from the threads::shared module like a mutex? - multithreading

Question

i'm using AnyEvent to trigger event every X minutes. Some process are long and the result to record in the database are sometimes long to record (more than 3 seconds sometimes). I want to be sure that there is only one function that access to my database the same time. So I use lock from the threads::shared module. Here is my code :
main.pl :
my $var :shared;
$var = 0;
my $w1 = AnyEvent->timer(after => 0, interval => 120, cb => sub {
my #targeted_users = TargetUsers::get_targeted_account_from_followers($dbh,$account,'myrhline');
TargetUsers::save_users_to_follow($dbh,'RH',$var,#targeted_users);
});
my $w2 = AnyEvent->timer(after => 0, interval => 120, cb => sub {
my #targeted_users2 = TargetUsers::get_targeted_account_from_followers($dbh,$account2,'actuel_rh');
TargetUsers::save_users_to_follow($dbh,'RH',$var,#targeted_users2);
});
AnyEvent::Loop::run;
TargetUsers :
sub save_users_to_follow{
my ($dbh,$topic,$var,#targeted_users) = #_;
lock($var); #I call lock($var) to lock the access to the database.
my #array1 = ();
$dbh->{AutoCommit} = 0;
my $sth2 = $dbh->prepare(
"UPDATE People_TO_FOLLOW
SET Pertinence = Pertinence + 1
WHERE Id_user = ?");
my $tuples_update = $sth2->execute_array(
{ ArrayTupleStatus => \my #tuple_status_update },
\#targeted_users,
);
if ($tuples_update) {
print "Successfully updated $tuples_update records\n";
}
else {
for my $tuple_1 (0..$#targeted_users) {
my $status_1 = $tuple_status_update[$tuple_1];
$status_1 = [0, "Skipped"] unless defined $status_1;
next unless ref $status_1;
printf "Failed to update (%s): %s\n",
$targeted_users[$tuple_1], $status_1->[1];
}
}
$sth2->finish();
my $sth = $dbh ->prepare(
"INSERT OR IGNORE INTO People_TO_FOLLOW(Id_user,Topic,Already_followed,Pertinence) VALUES (?,'$topic',0,1)");
my $tuples_insert = $sth->execute_array(
{ ArrayTupleStatus => \my #tuple_status_insert },
\#targeted_users,
);
if ($tuples_insert) {
print "Successfully inserted $tuples_insert records\n";
}
else {
for my $tuple_2 (0..$#targeted_users) {
my $status_2 = $tuple_status_insert[$tuple_2];
$status_2 = [0, "Skipped"] unless defined $status_2;
next unless ref $status_2;
printf "Failed to insert (%s): %s\n",
$targeted_users[$tuple_2], $status_2->[1];
}
}
$sth->finish();
$dbh->commit;
$dbh->{AutoCommit} = 1;
}
But I get this error : "lock can only be used on shared values"
Have you some idea please ? Thanks

Answer 1

You have two vars named $var, the one in main.pl, and the one in save_users_to_follow. The former is the shared variable, but you are trying to lock the latter.
Move the var from main to TargetUsers, or pass a reference to the lock var to save_users_to_follow.