linux-kernel - Re: [PATCH] staging: pi433: add descriptions for mutex locks

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Date:   Fri, 23 Mar 2018 16:38:50 +0100
From:   Marcus Wolf <marcus.wolf@...rthome-wolf.de>
To:     Valentin Vidic <Valentin.Vidic@...Net.hr>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Simon Sandström <simon@...anor.nu>,
        Marcus Wolf <linux@...f-Entwicklungen.de>,
        Luca Söthe <luca@...l.me>,
        Marcin Ciupak <marcin.s.ciupak@...il.com>,
        Michael Panzlaff <michael.panzlaff@....de>,
        Derek Robson <robsonde@...il.com>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: pi433: add descriptions for mutex locks

Hi Valentin,

I had no time to work on the code for monthes now and the memorisation
of my thoughts when I was programming that (approx. one year ago) is
quite pale.

As far as I remember, I read something, that the fifo has an integrated
protection, so no external protection is needed. But absolutely unsure.

If I will find some time within the next days, I'll have a look at the
code and try to recall.

But the most important thing already took place: We started thinking
about it :-)

Thanks,

Marcus

Am 23.03.2018 um 12:42 schrieb Valentin Vidic:
> On Fri, Mar 23, 2018 at 11:22:39AM +0100, Marcus Wolf wrote:
>> could you please decribe in short words, why you think, that hte lock
>> isn't obsolete?
>>
>> I wasn't sure, but close to remove the lock. That's why I putted the
>> comment.
> 
> Sure, if pi433_tx_thread runs on one CPU it might be possible
> to call pi433_write concurrently on another CPU and they would
> both modify tx_fifo.  But maybe there is some other protection
> in place that would prevent this?
> 

-- 
Smarthome-Wolf UG (haftungsbeschränkt)
Helene-Lange-Weg 23
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Amtsgericht München, HRB 223529
Umastzsteuer-ID: DE304719911
Geschäftsführer: Marcus Wolf