lkml.org 
[lkml]   [2022]   [Nov]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v8 08/11] tpm, tpm: Implement usage counter for locality
From


On 01.11.22 02:06, Jarkko Sakkinen wrote:
> On Tue, Oct 25, 2022 at 02:15:51AM +0200, Lino Sanfilippo wrote:

>> Actually thats on me, since it took me much too long to send the v8 after the v7 review.
>>
>> However the reason that we need a mutex here is that we not only increase or decrease
>> the locality_counter under the mutex, but also do the locality request and release by
>> writing to the ACCESS register. Since in the SPI case each communication over the spi bus
>> is protected by the bus_lock_mutex of the SPI device we must not hold a spinlock when doing
>> the register accesses.
>>
>> Concerning covering the whole tpm_tis_data struct:
>> Most structure elements are set once at driver startup but never changed at driver
>> runtime. So no locking needed for these. The only exception is "flags" and "locality_count"
>> whereby "flags" is accessed by atomic bit manipulating functions and thus
>> does not need extra locking. So "locality_count" is AFAICS the only element that needs to be
>> protected by the mutex.
>
> OK, but you should should still address this in commit message, e.g.
> by mentioning that in the case of SPI bus mutex is required because
> the bus itself needs to be locked in the mutex.
>
> I.e. this a claim, definitely not an argument: "Ensure thread-safety by
> protecting the counter with a mutex."
>

Ok, I will rephrase the commit message accordingly.
Thanks for the review!

Regards,
Lino

\
 
 \ /
  Last update: 2022-11-04 17:19    [W:0.077 / U:0.264 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site