Fix timeouts for android::base::WaitForProperty*
std::chrono doesn't handle integer overflow, so using
std::chrono::milliseconds::max() to indicate an infinite timeout is
not handled well in the current code. It causes an 'absolute_timeout'
earlier in time than 'now' and causes the associated WaitForProperty*
functions to return immediately.
Also, any duration_cast from relative_timeout to nanoseconds would
cause the same issue, as it would overflow in the conversion and
result in an invalid results.
This change prevents any duration_casts of relative_timeout to
nanoseconds and replaces the logic to wait on an absolute timeout with
logic that compares the time elapsed to the provided relative timeout.
This change also includes a test that std::chrono::milliseconds::max()
does not return immediately and that negative values do return immediately.
Test: Boot bullhead + libbase_test
Change-Id: I335bfa7ba71e86c20119a0ed46014cad44361162
diff --git a/base/properties.cpp b/base/properties.cpp
index 32c0128..816bca0 100644
--- a/base/properties.cpp
+++ b/base/properties.cpp
@@ -101,22 +101,24 @@
}
// TODO: chrono_utils?
-static void DurationToTimeSpec(timespec& ts, std::chrono::nanoseconds d) {
+static void DurationToTimeSpec(timespec& ts, const std::chrono::milliseconds 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();
}
+// TODO: boot_clock?
using AbsTime = std::chrono::time_point<std::chrono::steady_clock>;
-static void UpdateTimeSpec(timespec& ts,
- const AbsTime& timeout) {
+static void UpdateTimeSpec(timespec& ts, std::chrono::milliseconds relative_timeout,
+ const AbsTime& start_time) {
auto now = std::chrono::steady_clock::now();
- auto remaining_timeout = std::chrono::duration_cast<std::chrono::nanoseconds>(timeout - now);
- if (remaining_timeout < 0ns) {
+ auto time_elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(now - start_time);
+ if (time_elapsed >= relative_timeout) {
ts = { 0, 0 };
} else {
+ auto remaining_timeout = relative_timeout - time_elapsed;
DurationToTimeSpec(ts, remaining_timeout);
}
}
@@ -127,11 +129,7 @@
// Returns nullptr on timeout.
static const prop_info* WaitForPropertyCreation(const std::string& key,
const std::chrono::milliseconds& relative_timeout,
- AbsTime& absolute_timeout) {
- // TODO: boot_clock?
- auto now = std::chrono::steady_clock::now();
- absolute_timeout = now + relative_timeout;
-
+ const AbsTime& start_time) {
// Find the property's prop_info*.
const prop_info* pi;
unsigned global_serial = 0;
@@ -139,17 +137,16 @@
// The property doesn't even exist yet.
// Wait for a global change and then look again.
timespec ts;
- UpdateTimeSpec(ts, absolute_timeout);
+ UpdateTimeSpec(ts, relative_timeout, start_time);
if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return nullptr;
}
return pi;
}
-bool WaitForProperty(const std::string& key,
- const std::string& expected_value,
+bool WaitForProperty(const std::string& key, const std::string& expected_value,
std::chrono::milliseconds relative_timeout) {
- AbsTime absolute_timeout;
- const prop_info* pi = WaitForPropertyCreation(key, relative_timeout, absolute_timeout);
+ auto start_time = std::chrono::steady_clock::now();
+ const prop_info* pi = WaitForPropertyCreation(key, relative_timeout, start_time);
if (pi == nullptr) return false;
WaitForPropertyData data;
@@ -162,7 +159,7 @@
if (data.done) return true;
// It didn't, so wait for the property to change before checking again.
- UpdateTimeSpec(ts, absolute_timeout);
+ UpdateTimeSpec(ts, relative_timeout, start_time);
uint32_t unused;
if (!__system_property_wait(pi, data.last_read_serial, &unused, &ts)) return false;
}
@@ -170,8 +167,8 @@
bool WaitForPropertyCreation(const std::string& key,
std::chrono::milliseconds relative_timeout) {
- AbsTime absolute_timeout;
- return (WaitForPropertyCreation(key, relative_timeout, absolute_timeout) != nullptr);
+ auto start_time = std::chrono::steady_clock::now();
+ return (WaitForPropertyCreation(key, relative_timeout, start_time) != nullptr);
}
} // namespace base