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

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Date:	Tue, 17 Jun 2014 13:59:38 +0800
From:	"Yang,Wei" <Wei.Yang@...driver.com>
To:	"Yang,Wei" <Wei.Yang@...driver.com>, <Wei.Yang@...driver.com>,
	<stern@...land.harvard.edu>, <mina86@...a86.com>
CC:	<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 06/15/2014 10:42 AM, Yang,Wei wrote:
> Its v4, sorry for missing it in subject.

Alan, How about this version?

Cheers
Wei
>
> Regards
> Wei
> On 06/15/2014 10:40 AM, 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>
>> ---
>>   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;
>
>
>

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