[ARCHIVE DEBUG 07/13] audit_debug: instrument audit_cmd_mutex contention

[Richard Guy Briggs]

Debug contention for the audit_cmd_mutex including timing, stalling
and identies of holder and requestor.

Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
---
 kernel/audit.c |   18 +++++++++++++++++-
 1 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 93a466b..a586bf2 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1131,7 +1131,23 @@ static void audit_receive_skb(struct sk_buff *skb)
 /* Receive messages from netlink socket. */
 static void audit_receive(struct sk_buff  *skb)
 {
-	mutex_lock(&audit_cmd_mutex);
+	struct task_struct *owner;
+	unsigned long trytime = jiffies;
+	
+	pid_t pid = 0;
+
+	if (!mutex_trylock(&audit_cmd_mutex)) {
+		rcu_read_lock();
+		owner = ACCESS_ONCE(audit_cmd_mutex.owner);
+		if (owner)
+			pid = owner->pid;
+		rcu_read_unlock();
+		pr_warn("( %lu %lu )audit_cmd_mutex apid=%d Qlen=%d %d(%s) trying, already held by %d\n",
+			trytime, jiffies - trytime, audit_pid, skb_queue_len(&audit_skb_queue), current->pid, current->comm, pid);
+		mutex_lock(&audit_cmd_mutex);
+		pr_warn("( %lu %lu )audit_cmd_mutex apid=%d Qlen=%d %d(%s) acquired, released by %d\n",
+			trytime, jiffies - trytime, audit_pid, skb_queue_len(&audit_skb_queue), current->pid, current->comm, pid);
+	}
 	audit_receive_skb(skb);
 	mutex_unlock(&audit_cmd_mutex);
 }
-- 
1.7.1