netdev - Re: [PATCH net v2] net: wireless: marvell: mwifiex: fix sleep in atomic context bugs

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Message-ID: <4e778cb1.22654.180decbcb8e.Coremail.duoming@zju.edu.cn>
Date:   Fri, 20 May 2022 08:08:59 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "Jeff Johnson" <quic_jjohnson@...cinc.com>
Cc:     "Kalle Valo" <kvalo@...nel.org>, linux-kernel@...r.kernel.org,
        amitkarwar@...il.com, ganapathi017@...il.com,
        sharvari.harisangam@....com, huxinming820@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net v2] net: wireless: marvell: mwifiex: fix sleep in
 atomic context bugs

Hello,

On Thu, 19 May 2022 08:48:44 -0700 Jeff Johnson wrote:

> >>> There are sleep in atomic context bugs when uploading device dump
> >>> data on usb interface. The root cause is that the operations that
> >>> may sleep are called in fw_dump_timer_fn which is a timer handler.
> >>> The call tree shows the execution paths that could lead to bugs:
> >>>
> >>>     (Interrupt context)
> >>> fw_dump_timer_fn
> >>>    mwifiex_upload_device_dump
> >>>      dev_coredumpv(..., GFP_KERNEL)
> 
> just looking at this description, why isn't the simple fix just to 
> change this call to use GFP_ATOMIC?

Because change the parameter of dev_coredumpv() to GFP_ATOMIC could only solve
partial problem. The following GFP_KERNEL parameters are in /lib/kobject.c 
which is not influenced by dev_coredumpv().

 kobject_set_name_vargs
   kvasprintf_const(GFP_KERNEL, ...); //may sleep
   kstrdup(s, GFP_KERNEL); //may sleep

Best regards,
Duoming Zhou