linux-kernel - Re: [PATCH] hv: hv_fcopy: drop the obsolete message on transfer failure

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Message-ID: <87oasc69jk.fsf@vitty.brq.redhat.com>
Date:	Wed, 12 Nov 2014 10:41:03 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Dexuan Cui <decui@...rosoft.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org, olaf@...fle.de,
	apw@...onical.com, jasowang@...hat.com, kys@...rosoft.com,
	haiyangz@...rosoft.com
Subject: Re: [PATCH] hv: hv_fcopy: drop the obsolete message on transfer failure

Dexuan Cui <decui@...rosoft.com> writes:

> In the case the user-space daemon crashes, hangs or is killed, we
> need to down the semaphore, otherwise, after the daemon starts next
> time, the obsolete data in fcopy_transaction.message or
> fcopy_transaction.fcopy_msg will be used immediately.
>
> Cc: K. Y. Srinivasan <kys@...rosoft.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

> ---
>  drivers/hv/hv_fcopy.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
> index 23b2ce2..177122a 100644
> --- a/drivers/hv/hv_fcopy.c
> +++ b/drivers/hv/hv_fcopy.c
> @@ -86,6 +86,15 @@ static void fcopy_work_func(struct work_struct *dummy)
>  	 * process the pending transaction.
>  	 */
>  	fcopy_respond_to_host(HV_E_FAIL);
> +
> +	/* In the case the user-space daemon crashes, hangs or is killed, we
> +	 * need to down the semaphore, otherwise, after the daemon starts next
> +	 * time, the obsolete data in fcopy_transaction.message or
> +	 * fcopy_transaction.fcopy_msg will be used immediately.
> +	 */
> +	if (down_trylock(&fcopy_transaction.read_sema))
> +		pr_debug("FCP: failed to acquire the semaphore\n");
> +
>  }
>
>  static int fcopy_handle_handshake(u32 version)

-- 
  Vitaly
--
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