From: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
To: Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
Stefan Agner <stefan@agner.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
Wei Yongjun <weiyongjun1@huawei.com>,
Aaron Brice <aaron.brice@datasoft.com>,
Nicolae Rosia <nicolae_rosia@mentor.com>,
<linux-serial@vger.kernel.org>, Chris Healy <cphealy@gmail.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tty: serial: fsl_lpuart: fix del_timer_sync() vs timer routine deadlock
Date: Sat, 3 Dec 2016 12:36:31 +0530 [thread overview]
Message-ID: <9ee78fcd-7aca-e2d3-4df1-fe65a512a0f5@toradex.com> (raw)
In-Reply-To: <d858c7d2-c96c-f0dd-c5eb-bedd9187f8d8@cogentembedded.com>
On 12/03/2016 02:58 AM, Nikita Yushchenko wrote:
>>> Problem found via lockdep:
>>>
>>> - lpuart_set_termios() calls del_timer_sync(&sport->lpuart_timer) while
>>> holding sport->port.lock
>>>
>>> - sport->lpuart_timer routine is lpuart_timer_func() that calls
>>> lpuart_copy_rx_to_tty() that acquires same lock.
>>>
>>> To fix, move Rx DMA stopping out of lock, as it already is in other places
>>> in the same file.
>>>
>>> While at it, also make Rx DMA start/stop code to look the same is in
>>> other places in the same file.
>> Yeah I saw that too, never really came around to look closer into it.
>>
>> Thanks for looking into it.
>>
>> You removed the check whether there was an old configuration, I think
>> the idea of that was that we only resize DMA if it was configured
>> differently before...
> Per my code reading, checking for sport->lpuart_dma_rx_use should be
> enough, this flag will be set only if DMA was previously enabled,
The check is to make sure the reconfiguration of DMA is done only when
the baudrate is altered.
--
Bhuvan
>
>>> + if (sport->lpuart_dma_rx_use) {
>>> + if (!lpuart_start_rx_dma(sport)) {
>>> sport->lpuart_dma_rx_use = true;
>> No need to set to true here, it is guaranteed to be true at this point.
> I've seen this... However elsewhere in this file (namely in
> lpuart_resume(), in very similar situation, code is exactly the same,
> i.e. it sets sport->lpuart_dma_rx_use in both clauses. I thought it
> could be for a reason (i.e. for readability).
>
> Nikita
next prev parent reply other threads:[~2016-12-03 22:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-02 10:28 [PATCH] tty: serial: fsl_lpuart: fix del_timer_sync() vs timer routine deadlock Nikita Yushchenko
2016-12-02 18:05 ` Stefan Agner
2016-12-02 21:28 ` Nikita Yushchenko
2016-12-03 7:06 ` Bhuvanchandra DV [this message]
2016-12-03 8:55 ` Nikita Yushchenko
2016-12-03 10:06 ` Bhuvanchandra DV
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9ee78fcd-7aca-e2d3-4df1-fe65a512a0f5@toradex.com \
--to=bhuvanchandra.dv@toradex.com \
--cc=aaron.brice@datasoft.com \
--cc=cphealy@gmail.com \
--cc=gregkh@linuxfoundation.org \
--cc=jslaby@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=nicolae_rosia@mentor.com \
--cc=nikita.yoush@cogentembedded.com \
--cc=stefan@agner.ch \
--cc=weiyongjun1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).