linux-kernel - Re: [PATCH V3] firmware loader: Fix the race FW_STATUS_DONE is followed by class

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Message-ID: <CACVXFVM-NB0CvihhVMf3ravop2CQNApzrD0uZ9OwQCV0WQzYBA@mail.gmail.com>
Date:	Thu, 8 Nov 2012 17:57:15 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] firmware loader: Fix the race FW_STATUS_DONE is
 followed by class_timeout

On Thu, Nov 8, 2012 at 7:14 PM, Chuansheng Liu <chuansheng.liu@...el.com> wrote:
>
> There is a race as below when calling request_firmware():
> CPU1                                   CPU2
> write 0 > loading
> mutex_lock(&fw_lock)
> ...
> set_bit FW_STATUS_DONE                 class_timeout is coming
>                                        set_bit FW_STATUS_ABORT
> complete_all &completion
> ...
> mutex_unlock(&fw_lock)
>
> In this time, the bit FW_STATUS_DONE and FW_STATUS_ABORT are set,
> and request_firmware() will return failure due to condition in
> _request_firmware_load():
>         if (!buf->size || test_bit(FW_STATUS_ABORT, &buf->status))
>                 retval = -ENOENT;
>
> But from the above scenerio, it should be a successful requesting.
> So we need judge if the bit FW_STATUS_DONE is already set before
> calling fw_load_abort() in timeout function.
>
> As Ming's proposal, we need change the timer into sched_work to
> benefit from using &fw_lock mutex also.
>
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>

Acked-by: Ming Lei <ming.lei@...onical.com>

Thanks,
--
Ming Lei
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