From: Felipe Balbi <balbi@ti.com>
To: Alan Cox <alan@linux.intel.com>
Cc: <balbi@ti.com>, Marcel Holtmann <marcel@holtmann.org>,
Greg KH <gregkh@linuxfoundation.org>,
Muralidharan Karicheri <m-karicheri2@ti.com>,
<linux-bluetooth@vger.kernel.org>, <linux-serial@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: hci_ldsic nested locking problem
Date: Thu, 20 Mar 2014 12:16:22 -0500 [thread overview]
Message-ID: <20140320171621.GA2827@saruman.home> (raw)
In-Reply-To: <1395333736.22077.32.camel@acox1-desk.ger.corp.intel.com>
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On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> > Hi,
> >
> > when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> > taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> > tty->ops->write() to actually send the characters, but that call will
> > try to acquire the same port lock again.
> >
> > Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> > Am I correct to assume that ->write_wakeup() is supposed to *just*
> > wakeup the bottom half so we handle ->write() in another context ?
> >
> > Is it legal to call tty->ops->write() from within ->write_wakeup() ?
>
> It isn't because you might send all the bytes and go
>
> write
> write_wakeup
> write
> write wakeup
> ...
>
> and recurse
cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
you want this to be sorted out ?
--
balbi
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WARNING: multiple messages have this Message-ID (diff)
From: Felipe Balbi <balbi-l0cyMroinI0@public.gmane.org>
To: Alan Cox <alan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: balbi-l0cyMroinI0@public.gmane.org,
Marcel Holtmann <marcel-kz+m5ild9QBg9hUCZPvPmw@public.gmane.org>,
Greg KH
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
Muralidharan Karicheri
<m-karicheri2-l0cyMroinI0@public.gmane.org>,
linux-bluetooth-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Linux Kernel Mailing List
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: hci_ldsic nested locking problem
Date: Thu, 20 Mar 2014 12:16:22 -0500 [thread overview]
Message-ID: <20140320171621.GA2827@saruman.home> (raw)
In-Reply-To: <1395333736.22077.32.camel-wU3TRTJX3O1FGiH78xh5akvbDziVy8sZEvhb3Hwu1Ks@public.gmane.org>
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On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> > Hi,
> >
> > when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> > taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> > tty->ops->write() to actually send the characters, but that call will
> > try to acquire the same port lock again.
> >
> > Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> > Am I correct to assume that ->write_wakeup() is supposed to *just*
> > wakeup the bottom half so we handle ->write() in another context ?
> >
> > Is it legal to call tty->ops->write() from within ->write_wakeup() ?
>
> It isn't because you might send all the bytes and go
>
> write
> write_wakeup
> write
> write wakeup
> ...
>
> and recurse
cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
you want this to be sorted out ?
--
balbi
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[-- Type: application/pgp-signature, Size: 819 bytes --]
next prev parent reply other threads:[~2014-03-20 17:16 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-20 16:34 hci_ldsic nested locking problem Felipe Balbi
2014-03-20 16:34 ` Felipe Balbi
2014-03-20 16:42 ` Alan Cox
2014-03-20 16:42 ` Alan Cox
2014-03-20 17:06 ` Kodiak Furr
2014-03-20 17:16 ` Felipe Balbi [this message]
2014-03-20 17:16 ` Felipe Balbi
2014-03-20 17:29 ` Felipe Balbi
2014-03-20 17:29 ` Felipe Balbi
2014-03-20 17:34 ` Peter Hurley
2014-03-20 17:35 ` Felipe Balbi
2014-03-20 17:35 ` Felipe Balbi
2014-03-20 18:45 ` Greg KH
2014-03-20 18:45 ` Greg KH
2014-03-20 18:54 ` Peter Hurley
2014-03-20 17:31 ` Peter Hurley
2014-03-20 18:11 ` Felipe Balbi
2014-03-20 18:11 ` Felipe Balbi
2014-03-20 18:21 ` Peter Hurley
2014-03-20 18:25 ` Felipe Balbi
2014-03-20 18:25 ` Felipe Balbi
2014-03-20 19:01 ` Felipe Balbi
2014-03-20 19:01 ` Felipe Balbi
2014-03-20 19:03 ` Felipe Balbi
2014-03-20 19:03 ` Felipe Balbi
2014-03-20 19:16 ` Peter Hurley
2014-03-20 19:25 ` Felipe Balbi
2014-03-20 19:25 ` Felipe Balbi
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