pthread: Fix pthread_cond_timedwait returning early from timeout

The reason timeouts would sometimes happen before the abstime deadline was due
to rounding errors converting the timeout to milliseconds, and also because
vTaskDelay(1) only delays until the next tick which is less than one full tick
period.

Closes https://github.com/espressif/esp-idf/issues/6901

components/pthread/test/test_cxx_cond_var.cpp

@@ -4,13 +4,15 @@
 #include <chrono>
 #include <mutex>
 #include <atomic>
+#include <unistd.h>
+#include "freertos/FreeRTOS.h"
 #include "unity.h"
 
 #if __GTHREADS && __GTHREADS_CXX0X
 
-std::condition_variable cv;
-std::mutex cv_m;
-std::atomic<int> i{0};
+static std::condition_variable cv;
+static std::mutex cv_m;
+static std::atomic<int> i{0};
 
 static void waits(int idx, int timeout_ms)
 {
@@ -45,4 +47,52 @@ TEST_CASE("C++ condition_variable", "[std::condition_variable]")
 
     std::cout << "All threads joined\n";
 }
-#endif
+
+
+TEST_CASE("cxx: condition_variable can timeout", "[cxx]")
+{
+    std::condition_variable cv;
+    std::mutex mtx;
+    std::unique_lock<std::mutex> lck(mtx);
+    srand(99);
+    for (int i = 0; i < 10; ++i) {
+        usleep(rand() % 1000);
+        auto status = cv.wait_for(lck, std::chrono::milliseconds(200));
+        TEST_ASSERT_EQUAL(std::cv_status::timeout, status);
+    }
+}
+
+TEST_CASE("cxx: condition_variable timeout never before deadline", "[cxx]")
+{
+    using SysClock = std::chrono::system_clock;
+
+    std::mutex mutex;
+    std::condition_variable cond;
+    std::unique_lock<std::mutex> lock(mutex);
+
+    for (int i = 0; i < 25; ++i) {
+        auto timeout = std::chrono::milliseconds(portTICK_PERIOD_MS * (i+1));
+        auto deadline = SysClock::now() + timeout;
+
+        auto secs = std::chrono::time_point_cast<std::chrono::seconds>(deadline);
+        auto nsecs = std::chrono::duration_cast<std::chrono::nanoseconds>
+                (deadline - secs);
+        struct timespec ts = {
+                .tv_sec = static_cast<time_t>(secs.time_since_epoch().count()),
+                .tv_nsec = static_cast<long>(nsecs.count())};
+        int rc = ::pthread_cond_timedwait(cond.native_handle(),
+                                          lock.mutex()->native_handle(), &ts);
+        auto status = (rc == ETIMEDOUT) ? std::cv_status::timeout :
+                                          std::cv_status::no_timeout;
+        auto end = SysClock::now();
+        auto extra = end - deadline;
+        auto extra_us = extra / std::chrono::microseconds(1);
+        printf("timeout %lldms Extra time: %lldus, status: %s\n", timeout.count(), extra_us,
+               (status == std::cv_status::timeout) ? "timeout" : "no timeout");
+
+        // The timed wait should always return at least 1us after the timeout deadline
+        TEST_ASSERT_GREATER_THAN(0, extra_us);
+    }
+}
+
+#endif // __GTHREADS && __GTHREADS_CXX0X