Hi Johan,
On 13/07/15 12:07, Johan Hedberg wrote:
Hi Dean,
On Tue, Jun 23, 2015, Dean Jenkins wrote:
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1100,6 +1100,13 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
if (!sk)
return 0;
+ lock_sock(sk);
+
+ if (sk->sk_shutdown)
+ goto shutdown_already;
+
+ sk->sk_shutdown = SHUTDOWN_MASK;
+
/* prevent sk structure from being freed whilst unlocked */
sock_hold(sk);
@@ -1114,30 +1121,21 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
mutex_lock(&conn->chan_lock);
l2cap_chan_lock(chan);
- lock_sock(sk);
I guess this is at least part of the reason for the lockdep warnings we
started getting after your patches. The order of these locks should
always be l2cap_chan_lock() and then lock_sock(). Any other order
exposes us to potential deadlocks and the kernel lockdep system rightly
warns about it.
Do you think you'll be able to fix this as well as the missing
mutex_lock(&conn->chan_lock) issue this week? Otherwise we'll need to
consider reverting your patches since it's quite clear we can't make any
bluetooth-next pull requests with the current state of the tree.
I think it would be wise to revert the changes as I am unable to
guarantee that I get time to propose a fix during this week. I will try
to work on a v3 patchset based on your feedback.
The use of the
mutex_lock(&conn->chan_lock)
is troublesome because the underlying conn connection can disappear
whilst waiting for acks, that is why I eliminated the conn variable and
used chan->state instead. Is there an atomic method to check conn and
take the lock ?
I did some lockdep checking on our ARM kernel 3.14 but I get an
unrelated early lockdep report. This might be why we did not see any
lockdep issue for L2CAP. I think we might have a patch to force multiple
lockdeps to be reported, I will need to investigate.
I am trying to work out how to build l2cap-tester for a cross-compiled
ARM environment which was built from bitbake. I suspect I need to create
a bitbake recipe to build l2cap-tester, perhaps a recipe already exists
in Yocto ?
I now have a PTS dongle but I am having difficulties understanding how
to run any of the test cases. Do you have any hints ?
Thanks,
Regards,
Dean
--
Dean Jenkins
Embedded Software Engineer
Linux Transportation Solutions
Mentor Embedded Software Division
Mentor Graphics (UK) Ltd.
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