=head1 DESCRIPTION
-The C<Threads> module provides multithreading.
+The C<Thread> module provides multithreading support for perl.
+
+=head1 FUNCTIONS
+
+=over 8
+
+=item new \&start_sub
+
+=item new \&start_sub, LIST
+
+C<new> starts a new thread of execution in the referenced subroutine. The
+optional list is passed as parameters to the subroutine. Execution
+continues in both the subroutine and the code after the C<new> call.
+
+C<new Thread> returns a thread object representing the newly created
+thread.
+
+=item lock VARIABLE
+
+C<lock> places a lock on a variable until the lock goes out of scope. If
+the variable is locked by another thread, the C<lock> call will block until
+it's available. C<lock> is recursive, so multiple calls to C<lock> are
+safe--the variable will remain locked until the outermost lock on the
+variable goes out of scope.
+
+Locks on variables only affect C<lock> calls--they do I<not> affect normal
+access to a variable. (Locks on subs are different, and covered in a bit)
+If you really, I<really> want locks to block access, then go ahead and tie
+them to something and manage this yourself. This is done on purpose. While
+managing access to variables is a good thing, perl doesn't force you out of
+its living room...
+
+If a container object, such as a hash or array, is locked, all the elements
+of that container are not locked. For example, if a thread does a C<lock
+@a>, any other thread doing a C<lock($a[12])> won't block.
+
+You may also C<lock> a sub, using C<lock &sub>. Any calls to that sub from
+another thread will block until the lock is released. This behaviour is not
+equvalent to C<use attrs qw(locked)> in the sub. C<use attrs qw(locked)>
+serializes access to a subroutine, but allows different threads
+non-simultaneous access. C<lock &sub>, on the other hand, will not allow
+I<any> other thread access for the duration of the lock.
+
+Finally, C<lock> will traverse up references exactly I<one> level.
+C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not.
+
+=item async BLOCK;
+
+C<async> creates a thread to execute the block immediately following
+it. This block is treated as an anonymous sub, and so must have a
+semi-colon after the closing brace. Like C<new Thread>, C<async> returns a
+thread object.
+
+=item Thread->self
+
+The C<Thread-E<gt>self> function returns a thread object that represents
+the thread making the C<Thread-E<gt>self> call.
+
+=item Thread->list
+
+C<Thread-E<gt>list> returns a list of thread objects for all running and
+finished but un-C<join>ed threads.
+
+=item cond_wait VARIABLE
+
+The C<cond_wait> function takes a B<locked> variable as a parameter,
+unlocks the variable, and blocks until another thread does a C<cond_signal>
+or C<cond_broadcast> for that same locked variable. The variable that
+C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied.
+If there are multiple threads C<cond_wait>ing on the same variable, all but
+one will reblock waiting to reaquire the lock on the variable. (So if
+you're only using C<cond_wait> for synchronization, give up the lock as
+soon as possible)
+
+=item cond_signal VARIABLE
+
+The C<cond_signal> function takes a locked variable as a parameter and
+unblocks one thread that's C<cond_wait>ing on that variable. If more than
+one thread is blocked in a C<cond_wait> on that variable, only one (and
+which one is indeterminate) will be unblocked.
+
+If there are no threads blocked in a C<cond_wait> on the variable, the
+signal is discarded.
+
+=item cond_broadcast VARIABLE
+
+The C<cond_broadcast> function works similarly to C<cond_wait>.
+C<cond_broadcast>, though, will unblock B<all> the threads that are blocked
+in a C<cond_wait> on the locked variable, rather than only one.
+
+=back
+
+=head1 METHODS
+
+=over 8
+
+=item join
+
+C<join> waits for a thread to end and returns any values the thread exited
+with. C<join> will block until the thread has ended, though it won't block
+if the thread has already terminated.
+
+If the thread being C<join>ed C<die>d, the error it died with will be
+returned at this time. If you don't want the thread performing the C<join>
+to die as well, you should either wrap the C<join> in an C<eval> or use the
+C<eval> thread method instead of C<join>.
+
+=item eval
+
+The C<eval> method wraps an C<eval> around a C<join>, and so waits for a
+thread to exit, passing along any values the thread might have returned.
+Errors, of course, get placed into C<$@>.
+
+=item tid
+
+The C<tid> method returns the tid of a thread. The tid is a monotonically
+increasing integer assigned when a thread is created. The main thread of a
+program will have a tid of zero, while subsequent threads will have tids
+assigned starting with one.
+
+=head1 LIMITATIONS
+
+The sequence number used to assign tids is a simple integer, and no
+checking is done to make sure the tid isn't currently in use. If a program
+creates more than 2^32 - 1 threads in a single run, threads may be assigned
+duplicate tids. This limitation may be lifted in a future version of Perl.
=head1 SEE ALSO
projects / p5sagit/p5-mst-13.2.git / commitdiff