support suspend resume of fault injection

cxplat/cxplat_test/cxplat_fault_injection_test.cpp

@@ -102,6 +102,21 @@ TEST_CASE("fault_injection", "[fault_injection]")
     // Clear the fault injection state.
     cxplat_fault_injection_reset();
 
+    auto inject_fault_from_same_callsite = []() { return cxplat_fault_injection_inject_fault(); };
+
+    cxplat_fault_injection_suspend();
+    REQUIRE(cxplat_fault_injection_is_enabled() == true);
+    REQUIRE(inject_fault_from_same_callsite() == false);
+
+    cxplat_fault_injection_suspend();
+    cxplat_fault_injection_resume();
+    REQUIRE(inject_fault_from_same_callsite() == false);
+
+    cxplat_fault_injection_resume();
+    REQUIRE(inject_fault_from_same_callsite() == true);
+
+    cxplat_fault_injection_reset();
+
     for (_fault_injection_expected_outcome state = _fault_injection_expected_outcome::ExpectFault;
          state <= _fault_injection_expected_outcome::ExpectFaultDifferentCallsite;
          state = (_fault_injection_expected_outcome)((int)state + 1)) {

cxplat/inc/winuser/cxplat_fault_injection.h

@@ -6,6 +6,8 @@
 #ifndef CXPLAT_DEBUGGING_FEATURES_ENABLED
 #define cxplat_fault_injection_is_enabled() false
 #define cxplat_fault_injection_inject_fault() false
+#define cxplat_fault_injection_suspend() ((void)0)
+#define cxplat_fault_injection_resume() ((void)0)
 #else
 #include <stdbool.h>
 
@@ -50,6 +52,20 @@ cxplat_fault_injection_inject_fault() CXPLAT_NOEXCEPT;
 bool
 cxplat_fault_injection_is_enabled() CXPLAT_NOEXCEPT;
 
+/**
+ * @brief Suspend fault injection. Calls may be nested and must be matched by calls to
+ * cxplat_fault_injection_resume(). This function is thread safe.
+ */
+void
+cxplat_fault_injection_suspend() CXPLAT_NOEXCEPT;
+
+/**
+ * @brief Resume fault injection after a matching call to cxplat_fault_injection_suspend().
+ * This function is thread safe.
+ */
+void
+cxplat_fault_injection_resume() CXPLAT_NOEXCEPT;
+
 /**
  * @brief Reset fault injection. This function is thread safe.
  */

cxplat/src/cxplat_winuser/fault_injection.cpp

@@ -11,6 +11,7 @@
 #include <map>
 #include <mutex>
 #include <psapi.h>
+#include <shared_mutex>
 #include <sstream>
 #include <string>
 #include <tuple>
@@ -40,6 +41,12 @@ typedef class _cxplat_fault_injection
     bool
     inject_fault();
 
+    void
+    suspend();
+
+    void
+    resume();
+
     /**
      * @brief Reset the fault injection state, both in memory and on disk.
      */
@@ -139,6 +146,9 @@ typedef class _cxplat_fault_injection
      */
     std::mutex _mutex;
 
+    std::shared_mutex _suspension_mutex;
+    _Guarded_by_(_suspension_mutex) size_t _suspension_count = 0;
+
     size_t _stack_depth;
     _Guarded_by_(_mutex) std::vector<std::string> _last_fault_stack;
 
@@ -209,9 +219,30 @@ _cxplat_fault_injection::~_cxplat_fault_injection()
 bool
 _cxplat_fault_injection::inject_fault()
 {
+    std::shared_lock lock(_suspension_mutex);
+    if (_suspension_count > 0) {
+        return false;
+    }
     return is_new_stack();
 }
 
+void
+_cxplat_fault_injection::suspend()
+{
+    std::unique_lock lock(_suspension_mutex);
+    _suspension_count++;
+}
+
+void
+_cxplat_fault_injection::resume()
+{
+    std::unique_lock lock(_suspension_mutex);
+    CXPLAT_RUNTIME_ASSERT(_suspension_count > 0);
+    if (_suspension_count > 0) {
+        _suspension_count--;
+    }
+}
+
 void
 _cxplat_fault_injection::reset()
 {
@@ -419,6 +450,22 @@ cxplat_fault_injection_is_enabled() noexcept
     return _cxplat_fault_injection_singleton != nullptr;
 }
 
+void
+cxplat_fault_injection_suspend() noexcept
+{
+    if (_cxplat_fault_injection_singleton) {
+        _cxplat_fault_injection_singleton->suspend();
+    }
+}
+
+void
+cxplat_fault_injection_resume() noexcept
+{
+    if (_cxplat_fault_injection_singleton) {
+        _cxplat_fault_injection_singleton->resume();
+    }
+}
+
 void
 cxplat_fault_injection_reset() noexcept
 {