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This compliant solution uses notify_all() to signal all waiting threads instead of a single random thread. Only the run_step() thread code from the noncompliant code example is modified, as modified.
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#include <condition_variable>
#include <iostream>
#include <mutex>
#include <thread>
std::mutex mutex;
std::condition_variable cond;
void run_step(size_t myStep) {
static size_t currentStep = 0;
std::unique_lock<std::mutex> lk(mutex);
std::cout << "Thread " << myStep << " has the lock" << std::endl;
while (currentStep != myStep) {
std::cout << "Thread " << myStep << " is sleeping..." << std::endl;
cond.wait(lk);
std::cout << "Thread " << myStep << " woke up" << std::endl;
}
// Do processing ...
std::cout << "Thread " << myStep << " is processing..." << std::endl;
currentStep++;
// Signal ALL waiting tasks.
cond.notify_all();
std::cout << "Thread " << myStep << " is exiting..." << std::endl;
}
// ... main() unchanged ... |
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