feature/android c321eea5af5: Block profiling signals in the Android UI thread

[Po Lu]

branch: feature/android
commit c321eea5af535d102c5e1d2d7e95029ce6fee427
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Block profiling signals in the Android UI thread
    
    * java/org/gnu/emacs/EmacsNative.java (EmacsNative): New
    function `setupSystemThread'.
    * java/org/gnu/emacs/EmacsService.java (onCreate): Block all
    signals except for SIGBUS and SIGSEGV in the UI thread.
    * src/android.c (setupSystemThread): New function.
---
 java/org/gnu/emacs/EmacsNative.java  |  4 ++++
 java/org/gnu/emacs/EmacsService.java | 25 +++++++++++++++++++++++++
 src/android.c                        | 24 ++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/java/org/gnu/emacs/EmacsNative.java 
b/java/org/gnu/emacs/EmacsNative.java
index cb89cf6808a..2fcbf8b94ef 100644
--- a/java/org/gnu/emacs/EmacsNative.java
+++ b/java/org/gnu/emacs/EmacsNative.java
@@ -188,6 +188,10 @@ public final class EmacsNative
      KEYCODE_VOLUME_MUTE should be forwarded to Emacs.  */
   public static native boolean shouldForwardMultimediaButtons ();
 
+  /* Initialize the current thread, by blocking signals that do not
+     interest it.  */
+  public static native void setupSystemThread ();
+
 
 
   /* Input connection functions.  These mostly correspond to their
diff --git a/java/org/gnu/emacs/EmacsService.java 
b/java/org/gnu/emacs/EmacsService.java
index 48e39f8b355..96216e51cf4 100644
--- a/java/org/gnu/emacs/EmacsService.java
+++ b/java/org/gnu/emacs/EmacsService.java
@@ -25,6 +25,7 @@ import java.io.UnsupportedEncodingException;
 
 import java.util.List;
 
+import java.util.concurrent.Semaphore;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import android.graphics.Matrix;
@@ -211,6 +212,7 @@ public final class EmacsService extends Service
     final String filesDir, libDir, cacheDir, classPath;
     final double pixelDensityX;
     final double pixelDensityY;
+    final Semaphore signalSemaphore;
 
     SERVICE = this;
     handler = new Handler (Looper.getMainLooper ());
@@ -220,6 +222,7 @@ public final class EmacsService extends Service
     pixelDensityX = metrics.xdpi;
     pixelDensityY = metrics.ydpi;
     resolver = getContentResolver ();
+    signalSemaphore = new Semaphore (0);
 
     try
       {
@@ -248,11 +251,33 @@ public final class EmacsService extends Service
                                          cacheDir, (float) pixelDensityX,
                                          (float) pixelDensityY,
                                          classPath, EmacsService.this);
+
+             /* Wait for the signal mask to be set up in the UI
+                thread.  */
+
+             while (true)
+               {
+                 try
+                   {
+                     signalSemaphore.acquire ();
+                     break;
+                   }
+                 catch (InterruptedException e)
+                   {
+                     ;;
+                   }
+               }
            }
          }, extraStartupArgument,
          /* If any file needs to be opened, open it now.  */
          EmacsOpenActivity.fileToOpen);
        thread.start ();
+
+       /* Now that the thread has been started, block signals which
+          don't interest the current thread.  */
+
+       EmacsNative.setupSystemThread ();
+       signalSemaphore.release ();
       }
     catch (IOException exception)
       {
diff --git a/src/android.c b/src/android.c
index 92aab548180..681723124ee 100644
--- a/src/android.c
+++ b/src/android.c
@@ -3077,6 +3077,30 @@ NATIVE_NAME (answerQuerySpin) (JNIEnv *env, jobject 
object)
   android_answer_query_spin ();
 }
 
+
+
+/* System thread setup.  Android doesn't always block signals Emacs is
+   interested in from being received by the UI or render threads,
+   which can lead to problems when those signals then interrupt one of
+   those threads.  */
+
+JNIEXPORT void JNICALL
+NATIVE_NAME (setupSystemThread) (void)
+{
+  sigset_t sigset;
+
+  /* Block everything except for SIGSEGV and SIGBUS; those two are
+     used by the runtime.  */
+
+  sigfillset (&sigset);
+  sigaddset (&sigset, SIGSEGV);
+  sigaddset (&sigset, SIGBUS);
+
+  if (pthread_sigmask (SIG_BLOCK, &sigset, NULL))
+    __android_log_print (ANDROID_LOG_WARN, __func__,
+                        "pthread_sigmask: %s", strerror (errno));
+}
+
 #ifdef __clang__
 #pragma clang diagnostic pop
 #else