From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: [PATCH 2 of 2] xs: avoid pthread_join deadlock in
	xs_daemon_close
Date: Tue, 11 May 2010 15:03:47 -0700
Message-ID: <4BE9D443.20106@goop.org>
References: <4BE9D3B9.2050206@goop.org>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Xen-devel <xen-devel@lists.xensource.com>, Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>
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Doing a pthread_cancel and join on the reader thread while holding all
the request/reply/watch mutexes can deadlock if the thread needs to
take any of those mutexes to exit.  Kill off the reader thread before
taking any mutexes (which should be redundant if we're  single-threaded
at that point).

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff -r 84ee0559ddc1 tools/xenstore/xs.c
--- a/tools/xenstore/xs.c	Tue May 11 14:55:14 2010 -0700
+++ b/tools/xenstore/xs.c	Tue May 11 14:55:20 2010 -0700
@@ -260,10 +260,6 @@
 
 void xs_daemon_close(struct xs_handle *h)
 {
-	mutex_lock(&h->request_mutex);
-	mutex_lock(&h->reply_mutex);
-	mutex_lock(&h->watch_mutex);
-
 #ifdef USE_PTHREAD
 	if (h->read_thr_exists) {
 		pthread_cancel(h->read_thr);
@@ -271,6 +267,10 @@
 	}
 #endif
 
+	mutex_lock(&h->request_mutex);
+	mutex_lock(&h->reply_mutex);
+	mutex_lock(&h->watch_mutex);
+
         close_free_msgs(h);
 
 	mutex_unlock(&h->request_mutex);