Resumable tasks¶
[scheduler.resumable_tasks]
Functions to suspend task execution at a specific point and signal to resume it later.
// Defined in header <oneapi/tbb/task.h>
using oneapi::tbb::task::suspend_point = /* implementation-defined */;
template < typename Func > void oneapi::tbb::task::suspend( Func );
void oneapi::tbb::task::resume( oneapi::tbb::task::suspend_point );
Requirements:
The
Functype must meet the SuspendFunc requirements.
The oneapi::tbb::task::suspend function called within a running task suspends execution of the task and switches the thread to participate in other oneTBB parallel work.
This function accepts a user callable object with the current execution context oneapi::tbb::task::suspend_point as an argument.
The oneapi::tbb::task::suspend_point context tag must be passed to the oneapi::tbb::task::resume function to trigger a program execution at the suspended point.
The oneapi::tbb::task::resume function can be called at any point of an application, even on a separate thread.
In this regard, this function acts as a signal for the task scheduler.
Note
There are no guarantees that the same thread that called oneapi::tbb::task::suspend continues execution after the suspended point.
However, these guarantees are provided for the outermost blocking oneTBB calls
(such as oneapi::tbb::parallel_for and oneapi::tbb::flow::graph::wait_for_all) and oneapi::tbb::task_arena::execute calls.
Example¶
// Parallel computation region
oneapi::tbb::parallel_for(0, N, [&](int) {
// Suspend the current task execution and capture the context
oneapi::tbb::task::suspend([&] (oneapi::tbb::task::suspend_point tag) {
// Dedicated user-managed activity that processes async requests.
async_activity.submit(tag); // could be OpenCL/IO/Database/Network etc.
}); // execution will be resumed after this function
});
// Dedicated user-managed activity:
// Signal to resume execution of the task referenced by the oneapi::tbb::task::suspend_point
// from a dedicated user-managed activity
oneapi::tbb::task::resume(tag);