Chapter 40. Threads
Support for threads needs to be built into the Perl executable.
The pragma threads implements thread objects and the necessary operations for threads:
- async block
Starts a thread to execute the block. Returns the thread object.
threads->listReturns a list of joinable threads.
threads->new(sub [,args ])Creates a new thread that starts executing in the referenced subroutine. The args are passed to this subroutine. Returns the thread object.
threads->selfReturns an object representing the current thread.
threads->yieldThe current thread gives up the CPU in favor of other threads.
thread objects support the following methods:
- detach
Detaches a thread so it runs independently.
- equal (thread)
Returns true if the thread and thread are the same thread. You can also compare thread objects directly, using the
==operator.- join
Waits for the thread to complete. The value returned is the return value from the thread’s subroutine.
- tid
Returns the thread id of a thread.
The pragma threads::shared implements operations that enable variable sharing across threads:
- cond_broadcast variable
Unblocks all threads waiting for this variable. variable must be locked.
- cond_signal variable
Unblocks one thread that is waiting for this variable. variable must be locked.
- cond_wait variable
Waits for another thread to issue a cond_signal or cond_broadcast on the variable. variable must be locked and will be temporarily unlocked while waiting.
- lock variable
Locks a shared variable against concurrent access. The lock is automatically released when it goes out of scope.
- share variable
Marks the variable as shared.
