NAME

SYNOPSIS

 use Apache::Session::Lock::Semaphore;

 my $locker = Apache::Session::Lock::Semaphore->new;
 die "no semaphores" unless $locker;

 $locker->acquire_read_lock($ref);
 $locker->acquire_write_lock($ref);
 $locker->release_read_lock($ref);
 $locker->release_write_lock($ref);
 $locker->release_all_locks($ref);

DESCRIPTION

CONFIGURATION

To set the number of semaphores, you need to pass an argument in the usual Apache::Session style. The name of the argument is NSems, and the value is an integer power of 2. For example:

 tie %s, 'Apache::Session::Blah', $id, {NSems => 16};

You may also need to configure the semaphore key that this package uses. By default, it uses key 31818. You can change this using the argument SemaphoreKey:

 tie %s, 'Apache::Session::Blah', $id, {NSems => 16, SemaphoreKey => 42};

PROBLEMS

If you get an invalid argument message, that usually means that the system is unhappy with the number of semaphores that you requested. Try decreasing the number of semaphores. The semaphore blocks that this package creates are persistent until the system is rebooted, so if you request 8 semaphores one time and 16 semaphores the next, it won't work. Use the system commands ipcs and ipcrm to inspect and remove unwanted semphore blocks.

AUTHOR

SEE ALSO