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Date: Sun, 6 May 2007 20:46:49 +0530
From: "Satyam Sharma" <satyam.sharma@...il.com>
To: "Ray Lee" <ray-lk@...rabbit.org>, stern@...land.harvard.edu
Cc: LKML <linux-kernel@...r.kernel.org>,
"Pavel Machek" <pavel@...e.cz>, "Rafael J. Wysocki" <rjw@...k.pl>,
"Max Krasnyansky" <maxk@...lcomm.com>, marcel@...tmann.org,
"pm list" <linux-pm@...ts.linux-foundation.org>
Subject: [PATCH] make hci_notifier a blocking notifier (was Re: BUG: sleeping function called from invalid context at net/core/sock.c:1523)
On 5/6/07, Satyam Sharma <satyam.sharma@...il.com> wrote:
> Hi Ray,
>
> On 5/6/07, Ray Lee <ray-lk@...rabbit.org> wrote:
> > Upon resume (from suspend to RAM) of my laptop, I'm getting the
> > following. (Not a regression, it's been there a while.) This is under
> > 2.6.21. Everything *seems* fine afterward, but... <shrug> -- it's not
> > like I use bluetooth all that often.
> >
> > My laptop has the bluetooth adapter hooked via USB insternally, so
> > it's the hci_usb driver. Authors cc:d.
> >
> > [ 1.329537] BUG: sleeping function called from invalid context at
> > net/core/sock.c:1523
> > [ 1.329574] in_atomic():1, irqs_disabled():0
> > [ 1.329576] INFO: lockdep is turned off.
> > [ 1.329578]
> > [ 1.329578] Call Trace:
> > [ 1.329585] [<ffffffff8029cedc>] debug_show_held_locks+0x1c/0x30
> > [ 1.329598] [<ffffffff8020b2f5>] __might_sleep+0xe5/0xf0
> > [ 1.329603] [<ffffffff803cfdbc>] lock_sock_nested+0x2c/0x120
> > [ 1.329617] [<ffffffff881c9a6a>] :bluetooth:hci_sock_dev_event+0x4a/0xf0
> > [ 1.329627] [<ffffffff881c9ae7>] :bluetooth:hci_sock_dev_event+0xc7/0xf0
> > [ 1.329634] [<ffffffff80269cef>] notifier_call_chain+0x2f/0x50
> > [ 1.329639] [<ffffffff80269d49>] atomic_notifier_call_chain+0x39/0x70
> > [ 1.329649] [<ffffffff881c4d86>] :bluetooth:hci_notify+0x16/0x20
> > [ 1.329657] [<ffffffff881c5deb>] :bluetooth:hci_unregister_dev+0x5b/0x80
> > [ 1.329664] [<ffffffff8825e136>] :hci_usb:hci_usb_disconnect+0x56/0x90
> > [ 1.329683] [<ffffffff8801e0fe>] :usbcore:usb_unbind_interface+0x4e/0xa0
> > [ 1.329690] [<ffffffff80392e03>] __device_release_driver+0x93/0xc0
> > [ 1.329694] [<ffffffff803933e6>] device_release_driver+0x46/0x70
> > [ 1.329699] [<ffffffff80392638>] bus_remove_device+0x78/0x90
> > [ 1.329703] [<ffffffff80390697>] device_del+0x187/0x200
> > [ 1.329717] [<ffffffff8801b4d2>] :usbcore:usb_disable_device+0x82/0x110
> > [ 1.329731] [<ffffffff8801745a>] :usbcore:usb_disconnect+0xba/0x140
> > [ 1.329746] [<ffffffff88018440>] :usbcore:hub_thread+0x400/0xcc0
> > [ 1.329757] [<ffffffff80297970>] autoremove_wake_function+0x0/0x40
> > [ 1.329772] [<ffffffff88018040>] :usbcore:hub_thread+0x0/0xcc0
> > [ 1.329775] [<ffffffff802977a0>] keventd_create_kthread+0x0/0x90
> > [ 1.329781] [<ffffffff80233e73>] kthread+0xd3/0x110
> > [ 1.329784] [<ffffffff80228890>] schedule_tail+0x0/0xe0
> > [ 1.329791] [<ffffffff80260648>] child_rip+0xa/0x12
> > [ 1.329796] [<ffffffff80260200>] restore_args+0x0/0x30
> > [ 1.329802] [<ffffffff80233da0>] kthread+0x0/0x110
> > [ 1.329806] [<ffffffff8026063e>] child_rip+0x0/0x12
> > [ 1.329809]
>
> Hmmm ... net/bluetooth/hci_sock.c:hci_sock_dev_event() is calling
> lock_sock() which can sleep (while holding the hci_sk_list.lock
> read-write spinlock).
>
> Can't really convert hci_sk_list.lock to a rwsem as
> hci_sock_dev_event() is the notifier_call for hci_sock_nblock which is
> an atomic notifier and so executes in atomic context.
>
> We could convert hci_sock_nblock itself to a blocking notifier too,
> but then I'm not _that_ familiar with this code to do that myself.
>
> Anyway, this doesn't look like anything to do with suspend-resume.
> Perhaps you could try to send this on bluez-devel@...ts.sf.net or
> netdev@...r.kernel.org or something.
Well, it was a cool summer Sunday evening in Kanpur and ... I decided
to stay in the lab and investigate this :-(
Anyway, the hci_notifier is called from the following six call sites:
hci_dev_open() and hci_dev_close() -> both called from
hci_sock_ioctl() => both can sleep
hci_register_dev() and hci_unregister_dev() => again both are capable
of sleeping
hci_suspend_dev() and hci_resume_dev() -> called from the .suspend()
and .resume() of the hci_usb_driver, and again both of these can sleep
Is there any other reason why hci_notifier must be an atomic notifier?
(CC'ing Alan Stern just in case, apparently hci_notifier became atomic
when notifier chains were classified into atomic / blocking)
Patch below makes hci_notifier a blocking notifier. Compile-tested
only, I have no bluetooth hardware to run this, so let me know if this
would be wrong.
(Note that this only goes half-way in resolving this bug, because we
would also need to convert hci_sk_list.lock from rwlock to rwsem for
that. But that is not possible as other users of hci_sk_list.lock
_are_ atomic)
Satyam
---
Make hci_notifier a blocking notifier, as none of its users call it
from atomic context.
Signed-off-by: Satyam Sharma <ssatyam@....iitk.ac.in>
---
net/bluetooth/hci_core.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
---
diff -ruNp a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
--- a/net/bluetooth/hci_core.c 2007-04-26 08:38:32.000000000 +0530
+++ b/net/bluetooth/hci_core.c 2007-05-06 20:16:30.000000000 +0530
@@ -72,23 +72,23 @@ DEFINE_RWLOCK(hci_cb_list_lock);
struct hci_proto *hci_proto[HCI_MAX_PROTO];
/* HCI notifiers list */
-static ATOMIC_NOTIFIER_HEAD(hci_notifier);
+static BLOCKING_NOTIFIER_HEAD(hci_notifier);
/* ---- HCI notifications ---- */
int hci_register_notifier(struct notifier_block *nb)
{
- return atomic_notifier_chain_register(&hci_notifier, nb);
+ return blocking_notifier_chain_register(&hci_notifier, nb);
}
int hci_unregister_notifier(struct notifier_block *nb)
{
- return atomic_notifier_chain_unregister(&hci_notifier, nb);
+ return blocking_notifier_chain_unregister(&hci_notifier, nb);
}
static void hci_notify(struct hci_dev *hdev, int event)
{
- atomic_notifier_call_chain(&hci_notifier, event, hdev);
+ blocking_notifier_call_chain(&hci_notifier, event, hdev);
}
/* ---- HCI requests ---- */
-
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