Add timeout support to android::base::WaitForProperty.
Bug: http://b/35201172
Test: ran tests
Change-Id: I025aa0217dc94fabf0eb076b285a84866b00e741
diff --git a/base/include/android-base/properties.h b/base/include/android-base/properties.h
index e275fa2..e2324b7 100644
--- a/base/include/android-base/properties.h
+++ b/base/include/android-base/properties.h
@@ -23,6 +23,7 @@
#error Only bionic supports system properties.
#endif
+#include <chrono>
#include <limits>
#include <string>
@@ -58,8 +59,12 @@
// tell you whether or not your call succeeded. A `false` return value definitely means failure.
bool SetProperty(const std::string& key, const std::string& value);
-// Waits for the system property `key` to have the value `expected_value`, .
-void WaitForProperty(const std::string& key, const std::string& expected_value);
+// Waits for the system property `key` to have the value `expected_value`.
+// Times out after `relative_timeout`.
+// Returns true on success, false on timeout.
+bool WaitForProperty(const std::string& key,
+ const std::string& expected_value,
+ std::chrono::milliseconds relative_timeout);
} // namespace base
} // namespace android
diff --git a/base/properties.cpp b/base/properties.cpp
index 0f0f638..acd6c0f 100644
--- a/base/properties.cpp
+++ b/base/properties.cpp
@@ -21,10 +21,14 @@
#include <sys/system_properties.h>
#include <sys/_system_properties.h>
+#include <algorithm>
+#include <chrono>
#include <string>
#include <android-base/parseint.h>
+using namespace std::chrono_literals;
+
namespace android {
namespace base {
@@ -96,14 +100,41 @@
}
}
-void WaitForProperty(const std::string& key, const std::string& expected_value) {
+// TODO: chrono_utils?
+static void DurationToTimeSpec(timespec& ts, std::chrono::nanoseconds d) {
+ auto s = std::chrono::duration_cast<std::chrono::seconds>(d);
+ auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(d - s);
+ ts.tv_sec = s.count();
+ ts.tv_nsec = ns.count();
+}
+
+static void UpdateTimeSpec(timespec& ts,
+ const std::chrono::time_point<std::chrono::steady_clock>& timeout) {
+ auto now = std::chrono::steady_clock::now();
+ auto remaining_timeout = std::chrono::duration_cast<std::chrono::nanoseconds>(timeout - now);
+ if (remaining_timeout < 0ns) {
+ ts = { 0, 0 };
+ } else {
+ DurationToTimeSpec(ts, remaining_timeout);
+ }
+}
+
+bool WaitForProperty(const std::string& key,
+ const std::string& expected_value,
+ std::chrono::milliseconds relative_timeout) {
+ // TODO: boot_clock?
+ auto now = std::chrono::steady_clock::now();
+ std::chrono::time_point<std::chrono::steady_clock> absolute_timeout = now + relative_timeout;
+ timespec ts;
+
// Find the property's prop_info*.
const prop_info* pi;
unsigned global_serial = 0;
while ((pi = __system_property_find(key.c_str())) == nullptr) {
// The property doesn't even exist yet.
// Wait for a global change and then look again.
- global_serial = __system_property_wait_any(global_serial);
+ UpdateTimeSpec(ts, absolute_timeout);
+ if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return false;
}
WaitForPropertyData data;
@@ -112,10 +143,12 @@
while (true) {
// Check whether the property has the value we're looking for?
__system_property_read_callback(pi, WaitForPropertyCallback, &data);
- if (data.done) return;
+ if (data.done) return true;
- // It didn't so wait for it to change before checking again.
- __system_property_wait(pi, data.last_read_serial);
+ // It didn't, so wait for the property to change before checking again.
+ UpdateTimeSpec(ts, absolute_timeout);
+ uint32_t unused;
+ if (!__system_property_wait(pi, data.last_read_serial, &unused, &ts)) return false;
}
}
diff --git a/base/properties_test.cpp b/base/properties_test.cpp
index d8186be..c68c2f8 100644
--- a/base/properties_test.cpp
+++ b/base/properties_test.cpp
@@ -134,8 +134,19 @@
android::base::SetProperty("debug.libbase.WaitForProperty_test", "b");
});
- android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "a");
+ ASSERT_TRUE(android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "a", 1s));
flag = true;
- android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "b");
+ ASSERT_TRUE(android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "b", 1s));
thread.join();
}
+
+TEST(properties, WaitForProperty_timeout) {
+ auto t0 = std::chrono::steady_clock::now();
+ ASSERT_FALSE(android::base::WaitForProperty("debug.libbase.WaitForProperty_timeout_test", "a",
+ 200ms));
+ auto t1 = std::chrono::steady_clock::now();
+
+ ASSERT_GE(std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0), 200ms);
+ // Upper bounds on timing are inherently flaky, but let's try...
+ ASSERT_LT(std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0), 600ms);
+}