libpdx: Add service poke logic to ServiceUtility.

Consolidate PDX service poke logic (reload system props) in the
ServiceUtility class. This used by atrace to poke PDX services
during systrace.

Bug: 37432968
Test: build succeeds.
Change-Id: Ia650f81fd5d324529b70f8796c4efbf7b3117327
diff --git a/libs/vr/libpdx_default_transport/private/pdx/default_transport/service_utility.h b/libs/vr/libpdx_default_transport/private/pdx/default_transport/service_utility.h
index 22c6b3f..81bb17b 100644
--- a/libs/vr/libpdx_default_transport/private/pdx/default_transport/service_utility.h
+++ b/libs/vr/libpdx_default_transport/private/pdx/default_transport/service_utility.h
@@ -1,6 +1,8 @@
 #ifndef ANDROID_PDX_DEFAULT_TRANSPORT_SERVICE_UTILITY_H_
 #define ANDROID_PDX_DEFAULT_TRANSPORT_SERVICE_UTILITY_H_
 
+#include <ftw.h>
+
 #include <pdx/client.h>
 #include <pdx/default_transport/client_channel_factory.h>
 #include <pdx/service.h>
@@ -25,15 +27,59 @@
     return ClientChannelFactory::GetEndpointPath(endpoint_path);
   }
 
+  // Traverses the PDX service path space and sends a message to reload system
+  // properties to each service endpoint it finds along the way.
+  // NOTE: This method is used by atrace to poke PDX services. Please avoid
+  // unnecessary changes to this mechanism to minimize impact on atrace.
+  static bool PokeServices() {
+    const int kMaxDepth = 16;
+    const int result =
+        nftw(GetRootEndpointPath().c_str(), PokeService, kMaxDepth, FTW_PHYS);
+    return result == 0 ? true : false;
+  }
+
  private:
   friend BASE;
 
   ServiceUtility(const std::string& endpoint_path, int* error = nullptr)
-      : BASE(ClientChannelFactory::Create(endpoint_path)) {
+      : BASE(ClientChannelFactory::Create(endpoint_path), 0) {
     if (error)
       *error = Client::error();
   }
 
+  // Sends the sysprop_change message to the service at fpath, so it re-reads
+  // its system properties. Returns 0 on success or a negated errno code on
+  // failure.
+  // NOTE: This method is used by atrace to poke PDX services. Please avoid
+  // unnecessary changes to this mechanism to minimize impact on atrace.
+  static int PokeService(const char* fpath, const struct stat* /*sb*/,
+                         int typeflag, struct FTW* /*ftwbuf*/) {
+    const bool kIgnoreErrors = true;
+
+    if (typeflag == FTW_F) {
+      int error;
+      auto utility = ServiceUtility::Create(fpath, &error);
+      if (!utility) {
+        if (error != -ECONNREFUSED) {
+          ALOGE("ServiceUtility::PokeService: Failed to open %s: %s.", fpath,
+                strerror(-error));
+        }
+        return kIgnoreErrors ? 0 : error;
+      }
+
+      auto status = utility->ReloadSystemProperties();
+      if (!status) {
+        ALOGE(
+            "ServiceUtility::PokeService: Failed to send sysprop change to %s: "
+            "%s",
+            fpath, status.GetErrorMessage().c_str());
+        return kIgnoreErrors ? 0 : -status.error();
+      }
+    }
+
+    return 0;
+  }
+
   ServiceUtility(const ServiceUtility&) = delete;
   void operator=(const ServiceUtility&) = delete;
 };