[patch] possible fix for server deadlock

0001-fix-possible-server-deadlock-in-ih_sub_cancel.patch (text/plain), 2.04 KB, created by Per Pomsel on 2012-04-26 07:55:55 UTC

From cc14440eface093548cb3bc7814da11d9a99d283 Mon Sep 17 00:00:00 2001
From: Anssi Hannula <[e-mail]>
Date: Wed, 4 Jan 2012 00:23:55 +0200
Subject: [PATCH] fix possible server deadlock in ih_sub_cancel

ih_sub_foreach() calls ih_sub_cancel() while inotify_lock is locked.
However, ih_sub_cancel() locks it again, and locking GMutex recursively
causes undefined behaviour.

Fix that by removing locking from ih_sub_cancel() as ih_sub_foreach()
is its only user. Also make the function static so that it won't
accidentally get used by other files without locking (inotify-helper.h
is an internal server header).

This should fix the intermittent deadlocks I've been experiencing
causing KDE applications to no longer start, and probably also
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=542361
---
 server/inotify-helper.c |    7 ++-----
 server/inotify-helper.h |    1 -
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/server/inotify-helper.c b/server/inotify-helper.c
index d77203e..0789fa4 100644
--- a/server/inotify-helper.c
+++ b/server/inotify-helper.c
@@ -123,13 +123,11 @@ ih_sub_add (ih_sub_t * sub)
 
 /**
  * Cancels a subscription which was being monitored.
+ * inotify_lock must be held when calling.
  */
-gboolean
+static gboolean
 ih_sub_cancel (ih_sub_t * sub)
 {
-	G_LOCK(inotify_lock);
-
-
 	if (!sub->cancelled)
 	{
 		IH_W("cancelling %s\n", sub->pathname);
@@ -140,7 +138,6 @@ ih_sub_cancel (ih_sub_t * sub)
 		sub_list = g_list_remove (sub_list, sub);
 	}
 
-	G_UNLOCK(inotify_lock);
 	return TRUE;
 }
 
diff --git a/server/inotify-helper.h b/server/inotify-helper.h
index 5d3b6d0..d36b5fd 100644
--- a/server/inotify-helper.h
+++ b/server/inotify-helper.h
@@ -34,7 +34,6 @@ gboolean	 ih_startup		(event_callback_t ecb,
 					 found_callback_t fcb);
 gboolean	 ih_running		(void);
 gboolean	 ih_sub_add		(ih_sub_t *sub);
-gboolean	 ih_sub_cancel		(ih_sub_t *sub);
 
 /* Return FALSE from 'f' if the subscription should be cancelled */
 void		 ih_sub_foreach		(void *callerdata, gboolean (*f)(ih_sub_t *sub, void *callerdata));
-- 
1.7.7.2