linux-kernel - Re: [PATCH] TTY: n_gsm, fix false positive WARN

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Date:	Wed, 25 Nov 2015 18:32:40 +0800
From:	xinhui <xinhui@...ux.vnet.ibm.com>
To:	Jiri Slaby <jslaby@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	dvyukov@...gle.com, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...ux.intel.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH] TTY: n_gsm, fix false positive WARN_ON

hi, Jiri

On 2015/11/25 17:56, Jiri Slaby wrote:
> Hi,
>
> On 11/25/2015, 07:32 AM, xinhui wrote:
>>      This warning should blame on commit 5a640967 ("tty/n_gsm.c: fix a
>> memory leak in gsmld_open()").
>
> Oh, yes, I messed up the "Fixes" line then. It should write:
> Fixes: 5a640967 ("tty/n_gsm.c: fix a memory leak in gsmld_open()")
>
that's Okay. :)

>> I have one confusion. As there is field gsm->num to store the index of
>> gsm_mux[]. so in gsm_cleanup_mux(), why we still use for-loop to find
>> this mux?
>>
>> In error handle path, for example, the call trace in this patch, as we
>> failed to activate it and the
>> gsm->num is invalid(and the value is 0). we can just modify the codes
>> like below:
>>
>> if(gsm_mux[gsm->num] == gsm)
>> ....other work
>> else
>>      return;
>>
>> I think it would work, and the logic is correct. Or I just miss
>> something important?
>
> Yup, it looks like a cleanup. Could you prepare a separate patch for that?
>
yes, I will do that :)

> Something like this:
>          /* open failed before registering => nothing to do */
>          if (gsm_mux[gsm->num] != gsm)
>                return;
>          spin_lock(&gsm_mux_lock);
>          gsm_mux[gsm->num] = NULL;
>          spin_unlock(&gsm_mux_lock);
>
looks pretty good, thanks.

> thanks,
>
thanks
xinhui

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