linux-kernel - Re: [PATCH v3] USB:gadget: Fix a warning while loading g_mass

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Date:	Fri, 13 Jun 2014 14:22:59 +0800
From:	"Yang,Wei" <Wei.Yang@...driver.com>
To:	<Wei.Yang@...driver.com>, <stern@...land.harvard.edu>
CC:	<balbi@...com>, <mina86@...a86.com>, <andrzej.p@...sung.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<wei.yang@...driver.com>
Subject: Re: [PATCH v3] USB:gadget: Fix a warning while loading g_mass_storage

On 06/09/2014 02:19 PM, 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, because the spinlock isn't held
> at this point.
>
> Signed-off-by: Yang Wei <Wei.Yang@...driver.com>
> Signed-off-by: Alan Stern <stern@...land.harvard.edu>
> ---
>   drivers/usb/gadget/f_mass_storage.c |    6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> Hi Alan,
>
> Thanks for your review, there are a few changes in v3:
>
> 1) Fix a coding style issue.
> 2) Refine the commit log
>
> Regards
> Wei

Ping, Alan, What do you think of it?

Wei
>
> diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
> index b963939..0cd8f21 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;
>   
>   	/*
> @@ -2421,6 +2422,7 @@ static void handle_exception(struct fsg_common *common)
>   		}
>   		common->state = FSG_STATE_IDLE;
>   	}
> +	new_fsg = common->new_fsg;
>   	spin_unlock_irq(&common->lock);
>   
>   	/* Carry out any extra actions required for the exception */
> @@ -2460,8 +2462,8 @@ 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)
> +		do_set_interface(common, new_fsg);
> +		if (new_fsg)
>   			usb_composite_setup_continue(common->cdev);
>   		break;
>   

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