From: KY Srinivasan <kys@microsoft.com>
To: Dexuan Cui <decui@microsoft.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "driverdev-devel@linuxdriverproject.org" 
	<driverdev-devel@linuxdriverproject.org>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "apw@canonical.com" <apw@canonical.com>,
        "jasowang@redhat.com" <jasowang@redhat.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
Subject: RE: [PATCH] hv: hv_fcopy: drop the obsolete message on transfer
 failure
Thread-Topic: [PATCH] hv: hv_fcopy: drop the obsolete message on transfer
 failure
Thread-Index: AQHP/ixzoWqBLlree0aJYfe1XGjx8ZxonIcQ
Date: Wed, 19 Nov 2014 22:59:15 +0000
Message-ID: <BN1PR0301MB0707ED3958628389255649FCA0890@BN1PR0301MB0707.namprd03.prod.outlook.com>
References: <1415768606-28538-1-git-send-email-decui@microsoft.com>
In-Reply-To: <1415768606-28538-1-git-send-email-decui@microsoft.com>
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> -----Original Message-----
> From: devel [mailto:driverdev-devel-bounces@linuxdriverproject.org] On
> Behalf Of Dexuan Cui
> Sent: Tuesday, November 11, 2014 9:03 PM
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; driverdev-
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Cc: Haiyang Zhang
> Subject: [PATCH] hv: hv_fcopy: drop the obsolete message on transfer
> failure
> 
> 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@microsoft.com>
> Signed-off-by: Dexuan Cui <decui@microsoft.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");
> +
>  }

When the daemon is killed, we currently reset the state in the release function. Why can't we cleanup the semaphore state (initialize) here as well.

K. Y
> 
>  static int fcopy_handle_handshake(u32 version)
> --
> 1.9.1
> 
> _______________________________________________
> devel mailing list
> devel@linuxdriverproject.org
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
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