96 lines
2.2 KiB
C++
96 lines
2.2 KiB
C++
#include <chrono>
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#include <condition_variable>
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#include <cstdio>
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#include <random>
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#include <thread>
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std::default_random_engine g_random_engine{std::random_device{}()};
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std::uniform_int_distribution<> g_distribution{0, 3000000};
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std::condition_variable g_condition_variable;
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std::mutex g_mutex;
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int g_count;
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char *g_char_ptr = nullptr;
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void
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barrier_wait()
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{
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std::unique_lock<std::mutex> lock{g_mutex};
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if (--g_count > 0)
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g_condition_variable.wait(lock);
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else
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g_condition_variable.notify_all();
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}
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void
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do_bad_thing_with_location(char *char_ptr, char new_val)
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{
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*char_ptr = new_val;
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}
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uint32_t
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access_pool (bool flag = false)
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{
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static std::mutex g_access_mutex;
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if (!flag)
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g_access_mutex.lock();
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char old_val = *g_char_ptr;
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if (flag)
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do_bad_thing_with_location(g_char_ptr, old_val + 1);
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if (!flag)
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g_access_mutex.unlock();
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return *g_char_ptr;
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}
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void
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thread_func (uint32_t thread_index)
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{
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printf ("%s (thread index = %u) startng...\n", __FUNCTION__, thread_index);
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barrier_wait();
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uint32_t count = 0;
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uint32_t val;
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while (count++ < 15)
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{
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// random micro second sleep from zero to 3 seconds
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int usec = g_distribution(g_random_engine);
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printf ("%s (thread = %u) doing a usleep (%d)...\n", __FUNCTION__, thread_index, usec);
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std::this_thread::sleep_for(std::chrono::microseconds{usec});
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if (count < 7)
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val = access_pool ();
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else
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val = access_pool (true);
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printf ("%s (thread = %u) after usleep access_pool returns %d (count=%d)...\n", __FUNCTION__, thread_index, val, count);
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}
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printf ("%s (thread index = %u) exiting...\n", __FUNCTION__, thread_index);
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}
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int main (int argc, char const *argv[])
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{
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g_count = 4;
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std::thread threads[3];
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g_char_ptr = new char{};
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// Create 3 threads
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for (auto &thread : threads)
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thread = std::thread{thread_func, std::distance(threads, &thread)};
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printf ("Before turning all three threads loose...\n"); // Set break point at this line.
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barrier_wait();
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// Join all of our threads
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for (auto &thread : threads)
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thread.join();
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delete g_char_ptr;
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return 0;
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}
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