linux-kernel - Re: [PATCH 2/2] usb: gadget: f_fs: stop sleeping in ffs_func_eps

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Message-ID: <aab715ba-a98c-3463-6b72-5db1e4e955c2@huawei.com>
Date:   Sat, 8 Oct 2016 14:52:31 +0800
From:   Chen Yu <chenyu56@...wei.com>
To:     Michal Nazarewicz <mina86@...a86.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        John Stultz <john.stultz@...aro.org>
CC:     <wangbinghui@...ilicon.com>, Greg KH <gregkh@...uxfoundation.org>,
        "Amit Pundir" <amit.pundir@...aro.org>,
        Guodong Xu <guodong.xu@...aro.org>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 2/2] usb: gadget: f_fs: stop sleeping in
 ffs_func_eps_disable


On 2016/10/4 8:07, Michal Nazarewicz wrote:
> ffs_func_eps_disable is called from atomic context so it cannot sleep
> thus cannot grab a mutex.  Change the handling of epfile->read_buffer
> to use non-sleeping synchronisation method.
> 
> Reported-by: Chen Yu <chenyu56@...wei.com>
> Signed-off-by: Michał Nazarewicz <mina86@...a86.com>
> Fixes: 9353afbbfa7b ("buffer data from ‘oversized’ OUT requests")
> Tested-by: Chen Yu <chenyu56@...wei.com>
> ---
>  drivers/usb/gadget/function/f_fs.c | 109 +++++++++++++++++++++++++++++++------
>  1 file changed, 93 insertions(+), 16 deletions(-)
> 
> Compared to the previous version:
> • this one has a bit more comments (I feel like it’s a bad sign that
>   this needs so much documentation);
> • ffs_epfile_realese sets read_buffer to READ_BUFFER_DROP (which
>   doesn’t matter since on entry __ffs_epfile_read_buffered behaves
>   the same way when read_buffer is NULL or READ_BUFFER_DROP); and
> • __ffs_epfile_read_data will drop the temporary data if read_buffer
>   is READ_BUFFER_DROP (which may happen if ep is disabled between ep
>   request finishes and data is copied to user space).
> 
> Chen, John, if you could test this version as well, that would be
> swell.
> 

for both patches:

Tested-by: Chen Yu <chenyu56@...wei.com>

thanks again!
Chen Yu