linux-kernel - Re: USB device cannot be reconnected and khubd "blocked for more than 120 seconds"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.44L0.1301141302380.1782-100000@iolanthe.rowland.org>
Date:	Mon, 14 Jan 2013 13:04:27 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Ming Lei <ming.lei@...onical.com>,
	Alex Riesen <raa.lkml@...il.com>, Jens Axboe <axboe@...nel.dk>,
	USB list <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: USB device cannot be reconnected and khubd "blocked for more
 than 120 seconds"

On Mon, 14 Jan 2013, Linus Torvalds wrote:

> > - from view of driver, introducing async_synchronize_full() after
> > do_one_initcall() inside do_init_module() is like a sync probe
> > for drivers built as module, and cause this kind of deadlock easily.
> >
> > So could we revert the commit and fix the previous problems just
> > case by case? or other better fix?
> 
> There's no way in hell we take a "fix things one by one" approach.
> It's not going to work. And your suggestion seems to not do async
> discovery of devices in general, which is a *much* worse fix than
> anything else. It's just crazy.
> 
> But there are other approaches we might take. We might move the call to
> 
>     async_synchronize_full();
> 
> to other places. For example, maybe we're better off doing it at
> block/char device open instead?

How about skipping that call if the current thread is one of the async 
helpers?  Is it possible to detect when that happens?

Or maybe such a check should go inside async_synchronize_full() itself.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/