From c22e4adc07305d0ff39756843015be6b092cbcb6 Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Wed, 28 Jan 2015 22:08:49 -0500
Subject: Using SIOCOUTQ to flush output on client socket close caused a hard
 hang.

To replicate the problem:

(1) Check out the parent of this revision.

(2) Run "gpsd -n -N -D 3 /dev/ttyUSB0" substituting the device as needed.

(3) Run the following script in another window:

while true
do
  date
  ./gpspipe -n 3 -R -o /dev/null # hang if gpsd is sick
  ./gpspipe -d -R -o /dev/null
  sleep 2
  DELAY=$RANDOM      # 0-32K
  #usleep ${DELAY}00  # 0-3 seconds
  sleep  `echo "scale=6; $DELAY / 1000000" | bc`
  killall gpspipe
  #ps ax | grep gpspipe
done

(4) Run gpsmon in a third window.

gpsd will hang in 3-5 minutes, requiring kill -9, in the kernal hrtime
function.
---
 gpsd.c | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/gpsd.c b/gpsd.c
index eba0ecea..888dcc16 100644
--- a/gpsd.c
+++ b/gpsd.c
@@ -41,10 +41,6 @@
 #ifndef S_SPLINT_S
 #include <unistd.h>
 #endif /* S_SPLINT_S */
-#ifdef __linux__
-#include <sys/ioctl.h>		/* needed for ioctl(SIOCOUTQ) */
-#include <linux/sockios.h>	/* needed for ioctl(SIOCOUTQ) */
-#endif /* __linux__ */
 
 #include "gpsd_config.h"
 
@@ -553,19 +549,6 @@ static void detach_client(struct subscriber_t *sub)
     }
     c_ip = netlib_sock2ip(sub->fd);
     (void)shutdown(sub->fd, SHUT_RDWR);
-#ifdef __linux__
-    /*
-     * Delay the socket close that breaks the connection until
-     * all pending data has shipped.
-     */
-    for(;;) {
-	int outstanding;
-	ioctl(sub->fd, SIOCOUTQ, &outstanding);
-	if (!outstanding)
-	    break;
-	usleep(1000);
-    }
-#endif
     gpsd_report(&context.errout, LOG_SPIN,
 		"close(%d) in detach_client()\n",
 		sub->fd);
-- 
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