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Guarded Suspension applies a unique strategy to deal with mutation. It signals when it is done with its modification.<\/p>\n
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The guarded suspension basic variant combines a lock and a precondition that must be satisfied. If the precondition is not fulfilled, that checking thread puts itself to sleep. The checking thread uses a lock to avoid a race condition that may result in a data race or a deadlock.<\/p>\n
Various variants of the Guarded Suspension exist:<\/p>\n
I present in this post only the rough idea. For further information, I refer to posts I have already written.<\/p>\n
Let me start with the push principle.<\/p>\n
You often synchronize threads with a condition variable<\/a> or a future\/promise <\/a>pair. The condition variable or the promise sends the notification to the waiting thread. A promise has no <\/p>\n \u00a0<\/p>\n <\/p>\nnotify_one<\/code> or notify_all<\/code> member function. Typically, a valueless set_value<\/code> call is used to signal a notification. The following program snippets show the thread sending the notification and the waiting thread.<\/p>\n\n
\nvoid<\/span> waitingForWork<\/span>(){\n std::<\/span>cout <<<\/span> \"Worker: Waiting for work.\"<\/span> <<<\/span> '\\n'<\/span>;\n std::<\/span>unique_lock<<\/span>std::<\/span>mutex><\/span> lck(mutex_);\n condVar.wait(lck, []{ return<\/span> dataReady; });\n doTheWork();\n std::<\/span>cout <<<\/span> \"Work done.\"<\/span> <<<\/span> '\\n'<\/span>;\n}\n\nvoid<\/span> setDataReady<\/span>(){\n {\n std::<\/span>lock_guard<<\/span>std::<\/span>mutex><\/span> lck(mutex_);\n dataReady =<\/span> true<\/span>;\n }\n std::<\/span>cout <<<\/span> \"Sender: Data is ready.\"<\/span> <<<\/span> '\\n'<\/span>;\n condVar.notify_one();\n}\n<\/pre>\n<\/div>\n\n
\nvoid<\/span> waitingForWork<\/span>(std::<\/span>future<<\/span>void<\/span>>&&<\/span> fut){\n\n std::<\/span>cout <<<\/span> \"Worker: Waiting for work.\"<\/span> <<<\/span> std::<\/span>endl;\n fut.wait();\n doTheWork();\n std::<\/span>cout <<<\/span> \"Work done.\"<\/span> <<<\/span> std::<\/span>endl;\n\n}\n\nvoid<\/span> setDataReady<\/span>(std::<\/span>promise<<\/span>void<\/span>>&&<\/span> prom){\n\n std::<\/span>cout <<<\/span> \"Sender: Data is ready.\"<\/span> <<<\/span> std::<\/span>endl;\n prom.set_value();\n\n}\n<\/pre>\n<\/div>\nPull Principle<\/h3>\n