>> At boot time, probe function of multiple connected devices
>> (proprietary devices) execute simultaneously.
>
>What exactly do you mean here? How can probe happen "simultaneously"?
>The USB core prevents this, right?
I have observed two scenarios to call probe function:
Scenario #1: Driver inserted and attaching USB Device:
Yes, you are right, two probes at same time is not happening
in this scenario.
Scenario #2: USB Device attached and inserting Driver:
In this case probe has been called in context of insmod,
refer following code flow:
init -> usb_register_driver -> driver_register -> bus_add_driver ->
driver_attach -> bus_for_each_dev -> __driver_attach ->
driver_probe_device -> usb_probe_interface -> probe -> usb_register_dev
I have observed the crash in Scenario #2, as two probes executes at
same time in this scenario. And init_usb_class_mutex lock require to
prevent race condition.
>> And because of the following code path race condition happens:
>> probe->usb_register_dev->init_usb_class
>
>Why is this just showing up now, and hasn't been an issue for the decade
>or so this code has been around? What changed?
>
>> Tested with these changes, and problem has been solved.
>
>What changes?
Tested with my patch (i.e. locking with init_usb_class_mutex).
thanks,
ajay kaher
- Original Message -
Sender : gre...@linuxfoundation.org <gre...@linuxfoundation.org>
Date : 2017-01-31 12:31 (GMT+5:30)
Title : Re: Re: Subject: [PATCH v1] USB:Core: BugFix: Proper handling of Race
Condition when two USB class drivers try to call init_usb_class simultaneously
A: http://en.wikipedia.org/wiki/Top_post
Q: Were do I find info about this thing called top-posting?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
A: No.
Q: Should I include quotations after my reply?
http://daringfireball.net/2007/07/on_top
On Tue, Jan 31, 2017 at 05:21:46AM +, Ajay Kaher wrote:
>
>
> At boot time, probe function of multiple connected devices
> (proprietary devices) execute simultaneously.
What exactly do you mean here? How can probe happen "simultaneously"?
The USB core prevents this, right?
And what do you mean exactly by "(proprietary devices)"?
> And because of the following code path race condition happens:
> probe->usb_register_dev->init_usb_class
Why is this just showing up now, and hasn't been an issue for the decade
or so this code has been around? What changed?
> Tested with these changes, and problem has been solved.
What changes?
thanks,
greg k-h
Thanks and Regards,
Ajay Kaher