# Copyright (C) all contributors
# License: AGPL-3.0+
# Base class for per-inbox locking, subclassed by several
# only uses {lock_path} and {lockfh} fields
package PublicInbox::Lock;
use v5.12;
use Fcntl qw(LOCK_UN LOCK_EX O_RDWR O_CREAT);
use Carp qw(croak);
use PublicInbox::OnDestroy;
use Errno qw(EINTR);
use autodie qw(close sysopen syswrite);
sub xflock ($$) {
until (flock($_[0], $_[1])) { return if $! != EINTR }
1;
}
sub new { bless { lock_path => $_[1] }, $_[0] }
# we only acquire the flock if creating or reindexing;
# PublicInbox::Import already has the lock on its own.
sub lock_acquire {
my ($self) = @_;
my $fn = $self->{lock_path};
croak 'already locked '.($fn // '(undef)') if $self->{lockfh};
$fn // return;
sysopen(my $fh, $fn, O_RDWR|O_CREAT);
xflock($fh, LOCK_EX) or croak "LOCK_EX $fn: $!";
$self->{lockfh} = $fh;
}
sub lock_release {
my ($self, $wake) = @_;
my $fn = $self->{lock_path} // return;
my $fh = delete $self->{lockfh} or croak "not locked: $fn";
syswrite($fh, '.') if $wake;
xflock($fh, LOCK_UN) or croak "LOCK_UN $fn: $!";
close $fh; # may detect errors
}
# caller must use return value
sub lock_for_scope {
my ($self, @single_pid) = @_;
lock_acquire($self) or return; # lock_path not set
PublicInbox::OnDestroy->new(@single_pid, \&lock_release, $self);
}
sub lock_acquire_fast {
my $fh = $_[0]->{lockfh} or return lock_acquire($_[0]);
xflock($fh, LOCK_EX) or croak "LOCK_EX $_[0]->{lock_path}: $!";
}
sub lock_release_fast {
xflock($_[0]->{lockfh} // return, LOCK_UN) or
croak "LOCK_UN $_[0]->{lock_path}: $!"
}
# caller must use return value
sub lock_for_scope_fast {
my ($self, @single_pid) = @_;
lock_acquire_fast($self) or return; # lock_path not set
PublicInbox::OnDestroy->new(@single_pid, \&lock_release_fast, $self);
}
1;