Re-commit the new device locking, previously removed by a finger error.

1 files changed, 34 insertions, 23 deletions

diff --git a/serial.c b/serial.c
index 743c0283..eef91bd5 100644
--- a/serial.c
+++ b/serial.c
@@ -72,12 +72,13 @@ static sourcetype_t gpsd_classify(const char *path)
 #include <dirent.h>
 #include <ctype.h>
 
-static bool anyopen(const char *path)
+static int fusercount(const char *path)
 /* return true if any process has the specified path open */
 {
     DIR *procd, *fdd;
     struct dirent *procentry, *fdentry;
     char procpath[32], fdpath[64], linkpath[64];
+    int cnt = 0;
 
     if ((procd = opendir("/proc")) == NULL)
 	return false;
@@ -95,16 +96,15 @@ static bool anyopen(const char *path)
 	    if (readlink(fdpath, linkpath, sizeof(linkpath)) == -1)
 		continue;
 	    if (strcmp(linkpath, path) == 0) {
-		(void)closedir(fdd);
 		(void)closedir(procd);
 		return true;
 	    }
 	}
+	(void)closedir(fdd);
     }
-
-    (void)closedir(fdd);
     (void)closedir(procd);
-    return false;
+
+    return cnt;
 }
 #endif /* __linux__ */
 
@@ -375,20 +375,6 @@ int gpsd_open(struct gps_device_t *session)
     } else 
 #endif /* BLUEZ */
     {
-#ifdef __linux__
-	/*
-	 * Don't touch devices already opened by another process.  We
-	 * have to make an exception for ptys, which are intentionally
-	 * opened by another process on the master side, otherwise we'll
-	 * break all our regression tests.
-	 */
-	if (session->sourcetype != source_pty && anyopen(session->gpsdata.dev.path)) {
-            gpsd_report(LOG_ERROR, 
-			"%s already opened by another process\n",
-			session->gpsdata.dev.path);
-	    return -1;
-	}
-#endif /* __linux__ */
         if ((session->gpsdata.gps_fd =
 	     open(session->gpsdata.dev.path,
 		      (int)(mode | O_NONBLOCK | O_NOCTTY))) == -1) {
@@ -408,11 +394,36 @@ int gpsd_open(struct gps_device_t *session)
     }
 
     /*
-     * Try to block other processes from using this device while we
-     * have it open (later opens should return EBUSY).  Won't work
-     * against anything with root privileges, alas.
+     * Ideally we want to exclusion-lock the device before doing any reads.
+     * It would have been best to do this at open(2) time, but O_EXCL
+     * doesn't work wuthout O_CREAT.
+     *
+     * We have to make an exception for ptys, which are intentionally
+     * opened by another process on the master side, otherwise we'll
+     * break all our regression tests.
      */
-    (void)ioctl(session->gpsdata.gps_fd, TIOCEXCL);
+    if (session->sourcetype != source_pty) {
+	/*
+	 * Try to block other processes from using this device while we
+	 * have it open (later opens should return EBUSY).  Won't work
+	 * against anything with root privileges, alas.
+	 */
+	(void)ioctl(session->gpsdata.gps_fd, TIOCEXCL);
+
+#ifdef __linux__
+	/*
+	 * Don't touch devices already opened by another process.
+	 */
+	if (fusercount(session->gpsdata.dev.path) > 1) {
+            gpsd_report(LOG_ERROR, 
+			"%s already opened by another process\n",
+			session->gpsdata.dev.path);
+	    (void)close(session->gpsdata.gps_fd);
+	    session->gpsdata.gps_fd = -1;
+	    return -1;
+	}
+#endif /* __linux__ */
+    }
 
 #ifdef FIXED_PORT_SPEED
     session->saved_baud = FIXED_PORT_SPEED;