From: Ben Pfaff <blp@nicira.com>
Date: Thu, 8 Jan 2009 00:57:05 +0000 (-0800)
Subject: datapath: Avoid deadlock on dp_mutex versus kthread_stop().
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=12339817903642e1c9fe444cdf48ad31388337be;p=openvswitch

datapath: Avoid deadlock on dp_mutex versus kthread_stop().

When a datapath is deleted, del_dp() acquires dp_mutex and uses
kthread_stop() to wait for the dp_task to die.  Meanwhile, dp_task may
be waiting to acquire dp_mutex and won't die until it does so.

This commit fixes the problem by sending SIGKILL to dp_task before
call kthread_stop() and making dp_task give up if it receives a signal.
---

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 474d3ee2..efa84f9f 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -462,6 +462,7 @@ static void del_dp(struct datapath *dp)
 {
 	struct net_bridge_port *p, *n;
 
+	send_sig(SIGKILL, dp->dp_task, 0);
 	kthread_stop(dp->dp_task);
 
 	/* Drop references to DP. */
@@ -489,7 +490,8 @@ static int dp_maint_func(void *data)
 {
 	struct datapath *dp = (struct datapath *) data;
 
-	while (!kthread_should_stop()) {
+	allow_signal(SIGKILL);
+	while (!signal_pending(current)) {
 #ifdef SUPPORT_SNAT
 		struct net_bridge_port *p;
 
@@ -504,7 +506,10 @@ static int dp_maint_func(void *data)
 		chain_timeout(dp->chain);
 		msleep_interruptible(MAINT_SLEEP_MSECS);
 	}
-		
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule();
+	}
 	return 0;
 }
 
diff --git a/datapath/table-hash.c b/datapath/table-hash.c
index 2951722e..588b5f56 100644
--- a/datapath/table-hash.c
+++ b/datapath/table-hash.c
@@ -1,6 +1,6 @@
 /*
  * Distributed under the terms of the GNU GPL version 2.
- * Copyright (c) 2007, 2008 The Board of Trustees of The Leland 
+ * Copyright (c) 2007, 2008, 2009 The Board of Trustees of The Leland 
  * Stanford Junior University
  */
 
@@ -148,7 +148,8 @@ static int table_hash_timeout(struct datapath *dp, struct sw_table *swt)
 	unsigned int i;
 	int count = 0;
 
-	mutex_lock(&dp_mutex);
+	if (mutex_lock_interruptible(&dp_mutex))
+		return 0;
 	for (i = 0; i <= th->bucket_mask; i++) {
 		struct sw_flow **bucket = &th->buckets[i];
 		struct sw_flow *flow = *bucket;
diff --git a/datapath/table-linear.c b/datapath/table-linear.c
index 1d5e186d..bef58a6b 100644
--- a/datapath/table-linear.c
+++ b/datapath/table-linear.c
@@ -1,6 +1,6 @@
 /*
  * Distributed under the terms of the GNU GPL version 2.
- * Copyright (c) 2007, 2008 The Board of Trustees of The Leland 
+ * Copyright (c) 2007, 2008, 2009 The Board of Trustees of The Leland 
  * Stanford Junior University
  */
 
@@ -124,7 +124,8 @@ static int table_linear_timeout(struct datapath *dp, struct sw_table *swt)
 	struct sw_flow *flow;
 	int count = 0;
 
-	mutex_lock(&dp_mutex);
+	if (mutex_lock_interruptible(&dp_mutex))
+		return 0;
 	list_for_each_entry (flow, &tl->flows, node) {
 		int reason = flow_timeout(flow);
 		if (reason >= 0) {