Bug 397607 - "libXss.so.1 is unloaded while an XESetCloseDisplay callback is still registered" [p=karlt r+sr+a1.9=roc]

widget/src/gtk2/nsIdleServiceGTK.cpp

@@ -57,7 +57,7 @@ typedef XScreenSaverInfo* (*_XScreenSaverAllocInfo_fn)(void);
 typedef void (*_XScreenSaverQueryInfo_fn)(Display* dpy, Drawable drw,
                                           XScreenSaverInfo *info);
 
-static PRLibrary* xsslib = nsnull;
+static PRBool sInitialized = PR_FALSE;
 static _XScreenSaverQueryExtension_fn _XSSQueryExtension = nsnull;
 static _XScreenSaverAllocInfo_fn _XSSAllocInfo = nsnull;
 static _XScreenSaverQueryInfo_fn _XSSQueryInfo = nsnull;
@@ -68,13 +68,17 @@ NS_IMPL_ISUPPORTS1(nsIdleServiceGTK, nsIIdleService)
 nsIdleServiceGTK::nsIdleServiceGTK()
     : mXssInfo(nsnull)
 {
-    NS_ASSERTION(!xsslib, "created two instances of the idle service");
+}
+
+static void Initialize()
+{
+    sInitialized = PR_TRUE;
 #ifdef PR_LOGGING
-    if (!sIdleLog)
     sIdleLog = PR_NewLogModule("nsIIdleService");
 #endif
 
-    xsslib = PR_LoadLibrary("libXss.so.1");
+    // This will leak - See comments in ~nsIdleServiceGTK().
+    PRLibrary* xsslib = PR_LoadLibrary("libXss.so.1");
     if (!xsslib) // ouch.
     {
 #ifdef PR_LOGGING
@@ -97,39 +101,47 @@ nsIdleServiceGTK::nsIdleServiceGTK()
     if (!_XSSQueryInfo)
         PR_LOG(sIdleLog, PR_LOG_WARNING, ("Failed to get XSSQueryInfo!\n"));
 #endif
- 
 }
 
 nsIdleServiceGTK::~nsIdleServiceGTK()
 {
     if (mXssInfo)
         XFree(mXssInfo);
+
+// It is not safe to unload libXScrnSaver until each display is closed because
+// the library registers callbacks through XESetCloseDisplay (Bug 397607).
+// (Also the library and its functions are scoped for the file not the object.)
+#if 0
     if (xsslib) {
         PR_UnloadLibrary(xsslib);
         xsslib = nsnull;
     }
+#endif
 }
 
 NS_IMETHODIMP
 nsIdleServiceGTK::GetIdleTime(PRUint32 *aTimeDiff)
 {
     // Ask xscreensaver about idle time:
-    int event_base, error_base;
     *aTimeDiff = 0;
 
     // We might not have a display (cf. in xpcshell)
     Display *dplay = GDK_DISPLAY();
-    if (!dplay || !_XSSQueryExtension || !_XSSAllocInfo || !_XSSQueryInfo)
-    {
+    if (!dplay) {
 #ifdef PR_LOGGING
-        if (!dplay)
         PR_LOG(sIdleLog, PR_LOG_WARNING, ("No display found!\n"));
-        else
-            PR_LOG(sIdleLog, PR_LOG_WARNING, ("One of the Xss functions is missing!\n"));
 #endif
         return NS_ERROR_FAILURE;
     }
 
+    if (!sInitialized) {
+        Initialize();
+    }
+    if (!_XSSQueryExtension || !_XSSAllocInfo || !_XSSQueryInfo) {
+        return NS_ERROR_FAILURE;
+    }
+
+    int event_base, error_base;
     if (_XSSQueryExtension(dplay, &event_base, &error_base))
     {
         if (!mXssInfo)