linux-kernel - Re: [PATCH] USB:gadget: Fix a warning while loading g_mass

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Message-ID: <xa1ta99bwg81.fsf@mina86.com>
Date:	Tue, 17 Jun 2014 20:20:14 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Wei.Yang@...driver.com, stern@...land.harvard.edu
Cc:	wei.yang@...driver.com, balbi@...com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB:gadget: Fix a warning while loading g_mass_storage

On Sun, Jun 15 2014, Wei.Yang@...driver.com wrote:
> From: Yang Wei <Wei.Yang@...driver.com>
>
> While loading g_mass_storage module, the following warning
> is triggered.
>
> WARNING: at drivers/usb/gadget/composite.c:
> usb_composite_setup_continue: Unexpected call
> Modules linked in: fat vfat minix nls_cp437 nls_iso8859_1 g_mass_storage
> [<800179cc>] (unwind_backtrace+0x0/0x104) from [<80619608>] (dump_stack+0x20/0x24)
> [<80619608>] (dump_stack+0x20/0x24) from [<80025100>] (warn_slowpath_common+0x64/0x74)
> [<80025100>] (warn_slowpath_common+0x64/0x74) from [<800251cc>] (warn_slowpath_fmt+0x40/0x48)
> [<800251cc>] (warn_slowpath_fmt+0x40/0x48) from [<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage])
> [<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage]) from [<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage])
> [<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage]) from [<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage])
> [<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage]) from [<8004bc90>] (kthread+0x98/0x9c)
> [<8004bc90>] (kthread+0x98/0x9c) from [<8000faec>] (kernel_thread_exit+0x0/0x8)
>
> The root cause is that the existing code fails to take into
> account the possibility that common->new_fsg can change while
> do_set_interface() is running, so the value of common->new_fsg
> that gets tested after do_set_interface returns needs to be
> the same as the value used by do_set_interface.
>
> Signed-off-by: Yang Wei <Wei.Yang@...driver.com>
> Acked-by: Alan Stern <stern@...land.harvard.edu>

Acked-by: Michal Nazarewicz <mina86@...a86.com>

> ---
>  drivers/usb/gadget/f_mass_storage.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> Changes in v3 ----> v4
>
> move "new_fsg = common->new_fsg" out of comm->lock protection, and refine the commit log.
>
> Thanks
> Wei
>
> diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
> index b963939..a7e24c8 100644
> --- a/drivers/usb/gadget/f_mass_storage.c
> +++ b/drivers/usb/gadget/f_mass_storage.c
> @@ -2342,6 +2342,7 @@ static void handle_exception(struct fsg_common *common)
>  	struct fsg_buffhd	*bh;
>  	enum fsg_state		old_state;
>  	struct fsg_lun		*curlun;
> +	struct fsg_dev		*new_fsg;
>  	unsigned int		exception_req_tag;
>  
>  	/*
> @@ -2460,8 +2461,9 @@ static void handle_exception(struct fsg_common *common)
>  		break;
>  
>  	case FSG_STATE_CONFIG_CHANGE:
> -		do_set_interface(common, common->new_fsg);
> -		if (common->new_fsg)
> +		new_fsg = common->new_fsg;
> +		do_set_interface(common, new_fsg);
> +		if (new_fsg)
>  			usb_composite_setup_continue(common->cdev);
>  		break;

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--
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