linux-kernel - Re: [PATCH v5 2/2] mwifiex: fix sleep in atomic context bugs caused by dev

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Message-ID: <Yp5D7TRdNJ+bW1ud@google.com>
Date:   Mon, 6 Jun 2022 11:14:05 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Duoming Zhou <duoming@....edu.cn>
Cc:     linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        amitkarwar@...il.com, ganapathi017@...il.com,
        sharvari.harisangam@....com, huxinming820@...il.com,
        kvalo@...nel.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        johannes@...solutions.net, gregkh@...uxfoundation.org,
        rafael@...nel.org
Subject: Re: [PATCH v5 2/2] mwifiex: fix sleep in atomic context bugs caused
 by dev_coredumpv

On Fri, Jun 03, 2022 at 01:09:35PM +0800, Duoming Zhou wrote:
> There are sleep in atomic context bugs when uploading device dump
> data in mwifiex. The root cause is that dev_coredumpv could not
> be used in atomic contexts, because it calls dev_set_name which
> include operations that may sleep. The call tree shows execution
> paths that could lead to bugs:
...
> Fixes: f5ecd02a8b20 ("mwifiex: device dump support for usb interface")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> ---
> Changes in v5:
>   - Use delayed work to replace timer.
> 
>  drivers/net/wireless/marvell/mwifiex/init.c      | 10 ++++++----
>  drivers/net/wireless/marvell/mwifiex/main.h      |  2 +-
>  drivers/net/wireless/marvell/mwifiex/sta_event.c |  6 +++---
>  3 files changed, 10 insertions(+), 8 deletions(-)

Looks great! Thanks for working on this.

Reviewed-by: Brian Norris <briannorris@...omium.org>

Some small nitpicks below, but they're definitely not critical.

> diff --git a/drivers/net/wireless/marvell/mwifiex/init.c b/drivers/net/wireless/marvell/mwifiex/init.c
> index 88c72d1827a..3713f3e323f 100644
> --- a/drivers/net/wireless/marvell/mwifiex/init.c
> +++ b/drivers/net/wireless/marvell/mwifiex/init.c
> @@ -63,9 +63,11 @@ static void wakeup_timer_fn(struct timer_list *t)
>  		adapter->if_ops.card_reset(adapter);
>  }
>  
> -static void fw_dump_timer_fn(struct timer_list *t)
> +static void fw_dump_work(struct work_struct *work)
>  {
> -	struct mwifiex_adapter *adapter = from_timer(adapter, t, devdump_timer);
> +	struct mwifiex_adapter *adapter = container_of(work,
> +					struct mwifiex_adapter,
> +					devdump_work.work);

Super nitpicky: the hanging indent style seems a bit off. I typically
see people try to align to the first character after the parenthesis,
like:

	struct mwifiex_adapter *adapter = container_of(work,
						       struct mwifiex_adapter,
						       devdump_work.work);

It's not a clearly-specified style rule I think, so I definitely
wouldn't insist.

On the bright side: I think the clang-format rules (in .clang-format)
are getting better, so one can make some formatting decisions via tools
instead of opinion and close reading! Unfortunately, we probably can't
do that extensively and automatically, because I doubt people will love
all the reformatting because of all the existing inconsistent style.

Anyway, to cut to the chase: clang-format chooses moving to a new line:

	struct mwifiex_adapter *adapter =
		container_of(work, struct mwifiex_adapter, devdump_work.work);

More info if you're interested:
https://www.kernel.org/doc/html/latest/process/clang-format.html

>  
>  	mwifiex_upload_device_dump(adapter);
>  }

...

> diff --git a/drivers/net/wireless/marvell/mwifiex/main.h b/drivers/net/wireless/marvell/mwifiex/main.h
> index 332dd1c8db3..6530c6ee308 100644
> --- a/drivers/net/wireless/marvell/mwifiex/main.h
> +++ b/drivers/net/wireless/marvell/mwifiex/main.h
> @@ -1055,7 +1055,7 @@ struct mwifiex_adapter {

Nitpick: main.h is probably missing a lot of #includes, but you could
probably add <linux/workqueue.h> while you're at it.

Brian

>  	/* Device dump data/length */
>  	void *devdump_data;
>  	int devdump_len;
> -	struct timer_list devdump_timer;
> +	struct delayed_work devdump_work;
>  
>  	bool ignore_btcoex_events;
>  };