From 07c5e5661d1cf5717052ef5b92d50e1ecd178838 Mon Sep 17 00:00:00 2001
From: flamingcow <flamingcow@gmail.com>
Date: Sun, 12 May 2019 16:18:07 -0700
Subject: [PATCH] Tigher loop in KeepAlive; skip syscalls if overloaded

---
 firecgi      |  2 +-
 keepalive.cc | 13 +++++++------
 keepalive.h  |  7 ++++++-
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/firecgi b/firecgi
index 0ba446b..a39ef8e 160000
--- a/firecgi
+++ b/firecgi
@@ -1 +1 @@
-Subproject commit 0ba446bacb1cedaacea0f8347c0a068f652e04cf
+Subproject commit a39ef8e25dc2450b9219da67e37cfe158bd4a3ec
diff --git a/keepalive.cc b/keepalive.cc
index a4333c9..0c53128 100644
--- a/keepalive.cc
+++ b/keepalive.cc
@@ -8,12 +8,12 @@ namespace firesse {
 KeepAlive::KeepAlive(const std::chrono::nanoseconds& max_stale, Index* index)
 		: max_stale_(max_stale),
 		  index_(index),
-		  shutdown_(eventfd(0, 0)) {
-	PCHECK(shutdown_ >= 0) << "eventfd()";
+		  shutdown_fd_(eventfd(0, 0)) {
+	PCHECK(shutdown_fd_ >= 0) << "eventfd()";
 }
 
 KeepAlive::~KeepAlive() {
-	PCHECK(close(shutdown_) == 0);
+	PCHECK(close(shutdown_fd_) == 0);
 }
 
 void KeepAlive::Start() {
@@ -22,11 +22,11 @@ void KeepAlive::Start() {
 		constexpr auto num_fds = 1;
 		pollfd fds[num_fds] = {
 			{
-				.fd = shutdown_,
+				.fd = shutdown_fd_,
 				.events = POLLIN,
 			},
 		};
-		while (poll(fds, num_fds, timeout) <= 0) {
+		while (running_ && (timeout == 0 || poll(fds, num_fds, timeout) <= 0)) {
 			auto sleep = index_->WithStalest([](Stream* stream) {
 				stream->WriteRaw(":\n");
 			}, max_stale_);
@@ -38,8 +38,9 @@ void KeepAlive::Start() {
 void KeepAlive::Stop() {
 	CHECK(thread_.joinable());
 
+	running_ = false;
 	uint64_t shutdown = 1;
-	PCHECK(write(shutdown_, &shutdown, sizeof(shutdown)) == sizeof(shutdown));
+	PCHECK(write(shutdown_fd_, &shutdown, sizeof(shutdown)) == sizeof(shutdown));
 	thread_.join();
 }
 
diff --git a/keepalive.h b/keepalive.h
index fe75e4e..5396370 100644
--- a/keepalive.h
+++ b/keepalive.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <atomic>
 #include <thread>
 
 #include "index.h"
@@ -17,7 +18,11 @@ class KeepAlive {
   private:
 	const std::chrono::nanoseconds max_stale_;
 	Index* index_;
-	int shutdown_;
+
+	// Two shutdown mechanisms, one for if we're in a tight no-syscall loop,
+	// and one for if we're sleeping in poll()
+	int shutdown_fd_;
+	std::atomic<bool> running_ = true;
 
 	std::thread thread_;
 };