linux-kernel - Re: [PATCH] n_tty: Protect minimum_to

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Message-ID: <52938CC7.1000409@hurleysoftware.com>
Date:	Mon, 25 Nov 2013 12:45:43 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] n_tty: Protect minimum_to_wake reset for concurrent readers

On 11/25/2013 12:24 PM, Greg Kroah-Hartman wrote:
> On Mon, Nov 25, 2013 at 09:16:46AM -0800, Greg Kroah-Hartman wrote:
>> On Mon, Nov 25, 2013 at 12:12:52PM -0500, Peter Hurley wrote:
>>> On 11/25/2013 11:36 AM, Greg Kroah-Hartman wrote:
>>>> On Thu, Nov 07, 2013 at 02:01:57PM -0500, Peter Hurley wrote:
>>>>> With multiple, concurrent readers (each waiting to acquire the
>>>>> atomic_read_lock mutex), a departing reader may mistakenly reset
>>>>> minimum_to_wake after a new reader has already set a new value.
>>>>>
>>>>> Protect the minimum_to_wake reset with the atomic_read_lock critical
>>>>> section.
>>>>>
>>>>> Signed-off-by: Peter Hurley <peter@...leysoftware.com>
>>>>> ---
>>>>>   drivers/tty/n_tty.c | 4 ++--
>>>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> This patch doesn't apply to Linus's tree anymore (and hence, mine.)  Is
>>>> it needed for 3.13-final?  Or just 3.14-rc1?  Either way, can you
>>>> refresh it and resend?
>>>
>>> Hmmm, for me this applies cleanly to your tty-linus branch:
>>>
>>> peter@...r:~/src/kernels/tty$ git tree -10
>>> * c7df628 (HEAD, tty-linus) n_tty: Protect minimum_to_wake reset for concurrent readers
>>> * 3dcf344 (origin/tty-linus) TTY: amiserial, add missing platform check
>>> * dc1dc2f TTY: pmac_zilog, check existence of ports in pmz_console_init()
>>> * c284ee2 n_gsm: race between ld close and gsmtty open
>>> * f301412 tty/serial/8250: fix typo in help text
>>> * c77569d n_tty: Fix 4096-byte canonical reads
>>> * 6f22253 n_tty: Fix echo overrun tail computation
>>> * 42458f4 n_tty: Ensure reader restarts worker for next reader
>>> * 6ce4eac (tag: v3.13-rc1, origin/tty-next, origin/master, origin/HEAD) Linux 3.13-rc1
>>>
>>> I'll just resend it.
>>
>> Oh nevermind, it has leading extra spaces, which something added, I'll
>> go edit it by hand and fix it up, sorry for not noticing.
>
> And 'git am' handles this just fine, I was just testing it out first
> using 'patch' which didn't like the extra spaces, my fault.
>
> sorry for the noise,

Not a problem.

In fact, the interruption was fortuitous because I was testing an
unsubmitted patch which I'd hoped would fix the readline() paste
bug & bugzilla #55991.  When I tried to resend this patch with
git send-email, the 'Password:' prompt looped until I killed it.

Thanks for the test vector :)

Regards,
Peter Hurley

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