linux-kernel - Re: [PATCH] tpm: moves the delay_msec increment after sleep in tpm

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Message-Id: <95af65a1-e618-5cdf-fb81-56434f1aa973@linux.vnet.ibm.com>
Date:   Fri, 6 Apr 2018 14:03:37 +0530
From:   Nayna Jain <nayna@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.vnet.ibm.com,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        tpmdd@...horst.net, jgunthorpe@...idianresearch.com
Subject: Re: [PATCH] tpm: moves the delay_msec increment after sleep in
 tpm_transmit()



On 04/05/2018 03:42 PM, Jarkko Sakkinen wrote:
> On Mon, Apr 02, 2018 at 09:50:06PM +0530, Nayna Jain wrote:
>> Commit e2fb992d82c6 ("tpm: add retry logic") introduced a new loop to
>> handle the TPM2_RC_RETRY error. The loop retries the command after
>> sleeping for the specified time, which is incremented exponentially in
>> every iteration. This patch fixes the initial sleep to be the default
>> sleep time.
> I think I understand the code change but do not understand what the
> long description.

It tells that the first sleep is delay_msec * 2 and not delay_msec.

>
>> Fixes: commit e2fb992d82c6 ("tpm: add retry logic")
>> Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
>> Reviewed-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
>> ---
>>   drivers/char/tpm/tpm-interface.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index c43a9e28995e..6201aab374e6 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -587,7 +587,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>>   		 */
>>   		if (rc == TPM2_RC_TESTING && cc == TPM2_CC_SELF_TEST)
>>   			break;
>> -		delay_msec *= 2;
>> +
> Extra whitespace

I left just for clarity, but if not needed then I can remove it.

Thanks & Regards,
    - Nayna

>
>>   		if (delay_msec > TPM2_DURATION_LONG) {
>>   			if (rc == TPM2_RC_RETRY)
>>   				dev_err(&chip->dev, "in retry loop\n");
>> @@ -597,6 +597,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>>   			break;
>>   		}
>>   		tpm_msleep(delay_msec);
>> +		delay_msec *= 2;
>>   		memcpy(buf, save, save_size);
>>   	}
>>   	return ret;
>> -- 
>> 2.13.6
>>
> /Jarkko
>