On Sat, Dec 3, 2011 at 16:29, Thilo-Alexander Ginkel <thilo@xxxxxxxxxx> wrote:
> On Tue, Nov 29, 2011 at 16:14, Thilo-Alexander Ginkel <thilo@xxxxxxxxxx> wrote:
>> On Tue, Nov 29, 2011 at 14:23, Johan Hovold <jhovold@xxxxxxxxx> wrote:
>>>> page_fault
>>>> ? __ticket_spin_lock
>>>> default_spin_lock_flags
>>>> _raw_spin_lock_irqsave
>>>> tty_port_hangup
>>>> acm_tty_hangup [cdc_acm]
>>>> __tty_hangup
>>>> ? __tty_hangup
>>>> do_tty_hangup
>>>> process_one_work
>>>> worker_thread
>>>
>>> This could have been fixed by 5dc2470c602da (USB: cdc-acm: Fix disconnect() vs
>>> close() race).
>>>
>>>> $ uname -a
>>>> Linux orion 3.1.0-030100-generic #201110241006 SMP Mon Oct 24 14:07:10
>>>> UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
>>>
>>> Try updating to 3.1.4 which contains the above commit.
>>
>> Done. I'll let you know in case the problem reappears.
>
> Hm... Unfortunately, updating to 3.1.4 did not really help as my
> laptop is still sporadically locking up on suspend/resume iff a 3G
> connection via cdc_acm is actve at the point in time when the suspend
> happens.
I have got a question with regards to what data structure open_mutex
is supposed to protect:
In acm_tty_hangup, which triggers the crash, the mutex is only
acquired after tty_port_hangup has been called. Is this intended,
i.e., is it safe to access acm outside of the mutex?
555 static void acm_tty_hangup(struct tty_struct *tty)
556 {
557 »···struct acm *acm = tty->driver_data;
558 »···tty_port_hangup(&acm->port);
559 »···mutex_lock(&open_mutex);
560 »···acm_port_down(acm);
561 »···mutex_unlock(&open_mutex);
562 }
Another idea that came to my mind: If data transmission is in progress
when the suspend happens (as indicated by acm->transmitting), what are
the effects of returning EBUSY (just in case the suspend is an auto
suspend - under which circumstances do these happen?)? May this cause
trouble on resume?
1305 static int acm_suspend(struct usb_interface *intf, pm_message_t message)
1306 {
1307 »···struct acm *acm = usb_get_intfdata(intf);
1308 »···int cnt;
1309
1310 »···if (PMSG_IS_AUTO(message)) {
1311 »···»···int b;
1312
1313 »···»···spin_lock_irq(&acm->write_lock);
1314 »···»···b = acm->transmitting;
1315 »···»···spin_unlock_irq(&acm->write_lock);
1316 »···»···if (b)
1317 »···»···»···return -EBUSY;
1318 »···}
Thanks,
Thilo
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