[threading] Implement Posix HighResolutionTimer

Implement HighResolutionTimer for Posix by using native timers.
Callbacks are triggered with realtime interrupts if they are supported.
Create an enum to track user-defined interrupts as well as an initializer and
handler to register these interrupts per thread.
Add test cases for timers for both single and multiple.
Fix Sleep function to continue sleeping if interrupted by system.
Add local .gdbinit to ignore signal 34 which is used by high res timer

src/xenia/base/testing/threading_test.cc

@@ -62,8 +62,58 @@ TEST_CASE("TlsHandle") {
 }
 
 TEST_CASE("HighResolutionTimer") {
-  // TODO(bwrsandman):
-  REQUIRE(true);
+  // The wait time is 500ms with an interval of 50ms
+  // Smaller values are not as precise and fail the test
+  const auto wait_time = 500ms;
+
+  // Time the actual sleep duration
+  {
+    const auto interval = 50ms;
+    std::atomic<uint64_t> counter;
+    auto start = std::chrono::steady_clock::now();
+    auto cb = [&counter] { ++counter; };
+    auto pTimer = HighResolutionTimer::CreateRepeating(interval, cb);
+    Sleep(wait_time);
+    pTimer.reset();
+    auto duration = std::chrono::steady_clock::now() - start;
+
+    // Should have run as many times as wait_time / timer_interval plus or
+    // minus 1 due to imprecision of Sleep
+    REQUIRE(duration.count() >= wait_time.count());
+    auto ratio = static_cast<uint64_t>(duration / interval);
+    REQUIRE(counter >= ratio - 1);
+    REQUIRE(counter <= ratio + 1);
+  }
+
+  // Test concurrent timers
+  {
+    const auto interval1 = 100ms;
+    const auto interval2 = 200ms;
+    std::atomic<uint64_t> counter1;
+    std::atomic<uint64_t> counter2;
+    auto start = std::chrono::steady_clock::now();
+    auto cb1 = [&counter1] { ++counter1; };
+    auto cb2 = [&counter2] { ++counter2; };
+    auto pTimer1 = HighResolutionTimer::CreateRepeating(interval1, cb1);
+    auto pTimer2 = HighResolutionTimer::CreateRepeating(interval2, cb2);
+    Sleep(wait_time);
+    pTimer1.reset();
+    pTimer2.reset();
+    auto duration = std::chrono::steady_clock::now() - start;
+
+    // Should have run as many times as wait_time / timer_interval plus or
+    // minus 1 due to imprecision of Sleep
+    REQUIRE(duration.count() >= wait_time.count());
+    auto ratio1 = static_cast<uint64_t>(duration / interval1);
+    auto ratio2 = static_cast<uint64_t>(duration / interval2);
+    REQUIRE(counter1 >= ratio1 - 1);
+    REQUIRE(counter1 <= ratio1 + 1);
+    REQUIRE(counter2 >= ratio2 - 1);
+    REQUIRE(counter2 <= ratio2 + 1);
+  }
+
+  // TODO(bwrsandman): Check on which thread callbacks are executed when
+  // spawned from differing threads
 }
 
 TEST_CASE("Wait on Multiple Handles", "Wait") {