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->list

Returns 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->self

Returns an object representing the current thread.

threads->yield

The 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 ...

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