libhealthloop: Reduce the number of ScheduleBatteryUpdate() calls
Instead of calling ScheduleBatteryUpdate() every time a uevent has been
received, only call it after the netlink socket receive buffer has been
drained. This change is safe because the contents of the power supply
uevent messages is ignored.
A subtle change in this CL is that an additional call to
uevent_kernel_multicast_recv() is introduced after all the receive
buffer has been drained. In case of a receive buffer overflow, this
extra call will receive and clear the socket error (sk_err).
Bug: 362986353
Change-Id: Ic1c489dde3338f0142def743b4cd654363517486
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/health/utils/libhealthloop/HealthLoop.cpp b/health/utils/libhealthloop/HealthLoop.cpp
index ed0a43a..12c8b34 100644
--- a/health/utils/libhealthloop/HealthLoop.cpp
+++ b/health/utils/libhealthloop/HealthLoop.cpp
@@ -43,6 +43,8 @@
namespace hardware {
namespace health {
+static constexpr uint32_t kUeventMsgLen = 2048;
+
HealthLoop::HealthLoop() {
InitHealthdConfig(&healthd_config_);
awake_poll_interval_ = -1;
@@ -121,32 +123,39 @@
ScheduleBatteryUpdate();
}
-#define UEVENT_MSG_LEN 2048
-void HealthLoop::UeventEvent(uint32_t /*epevents*/) {
- // No need to lock because uevent_fd_ is guaranteed to be initialized.
-
- char msg[UEVENT_MSG_LEN + 2];
- char* cp;
- int n;
-
- n = uevent_kernel_multicast_recv(uevent_fd_, msg, UEVENT_MSG_LEN);
- if (n <= 0) return;
- if (n >= UEVENT_MSG_LEN) /* overflow -- discard */
- return;
-
- msg[n] = '\0';
- msg[n + 1] = '\0';
- cp = msg;
-
- while (*cp) {
- if (!strcmp(cp, "SUBSYSTEM=power_supply")) {
- ScheduleBatteryUpdate();
- break;
+// Returns true if and only if the battery statistics should be updated.
+bool HealthLoop::RecvUevents() {
+ bool update_stats = false;
+ for (;;) {
+ char msg[kUeventMsgLen + 2];
+ int n = uevent_kernel_multicast_recv(uevent_fd_, msg, kUeventMsgLen);
+ if (n <= 0) return update_stats;
+ if (n >= kUeventMsgLen) {
+ // too long -- discard
+ continue;
+ }
+ if (update_stats) {
+ continue;
}
- /* advance to after the next \0 */
- while (*cp++)
- ;
+ msg[n] = '\0';
+ msg[n + 1] = '\0';
+ for (char* cp = msg; *cp;) {
+ if (strcmp(cp, "SUBSYSTEM=power_supply") == 0) {
+ update_stats = true;
+ break;
+ }
+
+ /* advance to after the next \0 */
+ while (*cp++) {
+ }
+ }
+ }
+}
+
+void HealthLoop::UeventEvent(uint32_t /*epevents*/) {
+ if (RecvUevents()) {
+ ScheduleBatteryUpdate();
}
}
diff --git a/health/utils/libhealthloop/include/health/HealthLoop.h b/health/utils/libhealthloop/include/health/HealthLoop.h
index 1af7274..43c38dc 100644
--- a/health/utils/libhealthloop/include/health/HealthLoop.h
+++ b/health/utils/libhealthloop/include/health/HealthLoop.h
@@ -93,6 +93,7 @@
void WakeAlarmInit();
void WakeAlarmEvent(uint32_t);
void UeventInit();
+ bool RecvUevents();
void UeventEvent(uint32_t);
void WakeAlarmSetInterval(int interval);
void PeriodicChores();