From 637de21aca7b25b319ed59b84388b5bc4b03682b Mon Sep 17 00:00:00 2001
From: Greg Alexander <gitgreg@galexander.org>
Date: Wed, 17 Dec 2014 20:54:40 -0500
Subject: [PATCH] add locking to resolve some thread safety issues

---
 src/org/galexander/sshd/SimpleSSHD.java       | 49 +++++++++++++++++--
 .../galexander/sshd/SimpleSSHDService.java    | 16 ++----
 src/org/galexander/sshd/UpdaterThread.java    |  6 +--
 3 files changed, 48 insertions(+), 23 deletions(-)

diff --git a/src/org/galexander/sshd/SimpleSSHD.java b/src/org/galexander/sshd/SimpleSSHD.java
index b26193d..121ab6e 100644
--- a/src/org/galexander/sshd/SimpleSSHD.java
+++ b/src/org/galexander/sshd/SimpleSSHD.java
@@ -19,6 +19,7 @@ import java.io.BufferedReader;
 
 public class SimpleSSHD extends Activity
 {
+	private static final Object lock = new Object();
 	private EditText log_view;
 	private Button startstop_view;
 	public static SimpleSSHD curr = null;
@@ -34,14 +35,18 @@ public class SimpleSSHD extends Activity
 
 	public void onResume() {
 		super.onResume();
-		curr = this;
-		update_startstop();
+		synchronized (lock) {
+			curr = this;
+		}
+		update_startstop_prime();
 		updater = new UpdaterThread();
 		updater.start();
 	}
 
 	public void onPause() {
-		curr = null;
+		synchronized (lock) {
+			curr = null;
+		}
 		updater.interrupt();
 		super.onPause();
 	}
@@ -66,7 +71,7 @@ public class SimpleSSHD extends Activity
 		}
 	}
 
-	public void update_startstop() {
+	private void update_startstop_prime() {
 		if (SimpleSSHDService.is_started()) {
 			startstop_view.setText("STOP");
 			startstop_view.setTextColor(0xFF881111);
@@ -76,6 +81,23 @@ public class SimpleSSHD extends Activity
 		}
 	}
 
+	public static void update_startstop() {
+		Thread t = new Thread() {
+			public void run() {
+				synchronized (lock) {
+					if (curr != null) {
+						curr.update_startstop_prime();
+					}
+				}
+			}
+		};
+		synchronized (lock) {
+			if (curr != null) {
+				curr.runOnUiThread(t);
+			}
+		}
+	}
+
 	public void startstop_clicked(View v) {
 		Intent i = new Intent(this, SimpleSSHDService.class);
 		if (SimpleSSHDService.is_started()) {
@@ -84,7 +106,7 @@ public class SimpleSSHD extends Activity
 		startService(i);
 	}
 
-	public void update_log() {
+	private void update_log_prime() {
 		String[] lines = new String[50];
 		int curr_line = 0;
 		boolean wrapped = false;
@@ -118,4 +140,21 @@ public class SimpleSSHD extends Activity
 		log_view.setText(output);
 		log_view.setSelection(output.length());
 	}
+
+	public static void update_log() {
+		Thread t = new Thread() {
+			public void run() {
+				synchronized (lock) {
+					if (curr != null) {
+						curr.update_log_prime();
+					}
+				}
+			}
+		};
+		synchronized (lock) {
+			if (curr != null) {
+				curr.runOnUiThread(t);
+			}
+		}
+	}
 }
diff --git a/src/org/galexander/sshd/SimpleSSHDService.java b/src/org/galexander/sshd/SimpleSSHDService.java
index a4a816b..4e3fae0 100644
--- a/src/org/galexander/sshd/SimpleSSHDService.java
+++ b/src/org/galexander/sshd/SimpleSSHDService.java
@@ -34,7 +34,7 @@ public class SimpleSSHDService extends Service {
 			return START_STICKY;
 		} else {
 			stop_sshd();
-			update_activity();
+			SimpleSSHD.update_startstop();
 			stopSelf();
 /* XXX - need stopForeground() too ? */
 			return START_NOT_STICKY;
@@ -75,21 +75,11 @@ public class SimpleSSHDService extends Service {
 					if (sshd_pid == pid) {
 						sshd_pid = 0;
 					}
-					update_activity();
+					SimpleSSHD.update_startstop();
 				}
 			}).start();
 		}
-		update_activity();
-	}
-
-	private static void update_activity() {
-		if (SimpleSSHD.curr != null) {
-			SimpleSSHD.curr.runOnUiThread(new Runnable() {
-				public void run() {
-					SimpleSSHD.curr.update_startstop();
-				}
-			});
-		}
+		SimpleSSHD.update_startstop();
 	}
 
 	private static void read_pidfile() {
diff --git a/src/org/galexander/sshd/UpdaterThread.java b/src/org/galexander/sshd/UpdaterThread.java
index 40446c8..152084e 100644
--- a/src/org/galexander/sshd/UpdaterThread.java
+++ b/src/org/galexander/sshd/UpdaterThread.java
@@ -18,11 +18,7 @@ public class UpdaterThread extends Thread {
 			long mod = f.lastModified();
 			long len = f.length();
 			if ((mod != lastmod) || (len != lastlen)) {
-				SimpleSSHD.curr.runOnUiThread(new Thread() {
-					public void run() {
-						SimpleSSHD.curr.update_log();
-					}
-				});
+				SimpleSSHD.update_log();
 				lastmod = mod;
 				lastlen = len;
 			}