From f52d11e86cd51acde2406a38f9049c0acf462164 Mon Sep 17 00:00:00 2001
From: Earnestly <zibeon@gmail.com>
Date: Sat, 13 Jun 2015 23:56:51 +0100
Subject: [PATCH] Fix two corner cases which result in deadlocks.

This patch attempts to fix two corner cases which can result in hhpc
becoming deadlocked, <https://github.com/aktau/hhpc/issues/9>.

The first checks for the case where nanosleep() is interrupted which
would set working to 0 and as hhpc never recovers from this case, the
program will lockup indefinitely.  Instead we resume where we left of if
encountering EINTR.

The second fix is a bit of a hack; on rare occasions the select() call
in waitForMotion can seemingly block and practically never recover (I
didn't wait for more than one hour).

Instead I added a timeout to the select call, based on the gIdleTimeout
value if it is greater than 1, otherwise it uses a 3 second delay.
(This implies you can set a timeout of 2 seconds and have a 2 second
timeout.)

This doesn't really solve the issue of why select is getting stuck but
does allow hhpc to recover and prevent it from holding the mouse
hostage.
---
 hhpc.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/hhpc.c b/hhpc.c
index f106f7f..8ed7196 100644
--- a/hhpc.c
+++ b/hhpc.c
@@ -38,6 +38,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <errno.h>
 
 static int gIdleTimeout = 1;
 static int gVerbose     = 0;
@@ -90,8 +91,11 @@ static void delay(time_t sec, long msec) {
     sleep.tv_sec  = sec;
     sleep.tv_nsec = (msec % 1000) * 1000 * 1000;
 
-    if (nanosleep(&sleep, NULL) == -1) {
-        signalHandler(0);
+    while (nanosleep(&sleep, &sleep) != 0) {
+        if (errno == EINTR)
+            continue;
+        else
+            signalHandler(0);
     }
 }
 
@@ -158,6 +162,9 @@ static int grabPointer(Display *dpy, Window win, Cursor cursor, unsigned int mas
 }
 
 static void waitForMotion(Display *dpy, Window win, int timeout) {
+    struct timeval sleep;
+    sleep.tv_sec = (timeout <= 1) ? 3 : timeout;
+
     int ready = 0;
     int xfd   = ConnectionNumber(dpy);
 
@@ -193,7 +200,13 @@ static void waitForMotion(Display *dpy, Window win, int timeout) {
          * is interruptible by signals, which allows ctrl+c to work. If we
          * were to just use XNextEvent() (which blocks), ctrl+c would not
          * work. */
-        ready = select(xfd + 1, &fds, NULL, NULL, NULL);
+        if ((ready = select(xfd + 1, &fds, NULL, NULL, &sleep)) == -1) {
+            if (working) perror("hhpc: error while select()'ing");
+        }
+
+        if (ready == 0) {
+            if (gVerbose) fprintf(stderr, "hhpc: timeout\n");
+        }
 
         if (ready > 0) {
             if (gVerbose) fprintf(stderr, "hhpc: event received, ungrabbing and sleeping\n");
@@ -211,12 +224,6 @@ static void waitForMotion(Display *dpy, Window win, int timeout) {
 
             delay(timeout, 0);
         }
-        else if (ready == 0) {
-            if (gVerbose) fprintf(stderr, "hhpc: timeout\n");
-        }
-        else {
-            if (working) perror("hhpc: error while select()'ing");
-        }
     }
 
     XUngrabPointer(dpy, CurrentTime);