linux-kernel - RE: Re: [PATCH] pps: add epoll support

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Message-ID: <11965b8b6101487996df902d35ba2ea3@diehl.com>
Date: Tue, 25 Feb 2025 17:34:04 +0100 (CET)
From: Denis OSTERLAND-HEIM <denis.osterland@...hl.com>
To: Rodolfo Giometti <giometti@...eenne.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: Re: [PATCH] pps: add epoll support

Hi,

> -----Original Message-----
> From: Rodolfo Giometti <giometti@...eenne.com> 
> Sent: Tuesday, February 25, 2025 3:24 PM
> To: Denis OSTERLAND-HEIM <denis.osterland@...hl.com>
> Cc: linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] pps: add epoll support
>  
[snip]
> 
> > If I start multiple user space programs data races are visible.
> > 
> > ```
> > # for i in 0 1 2 3 4 5 6; do PpsPollTest /dev/pps1 > log$i & done
> > # sleep 6
> > # tail log*
> > ==> log0 <==
> > timeout
> > assert: 196
> > time: 1520599554.276752928
> > assert: 197
> > time: 1520599555.300692704
> 
> This is the same behavior we have when working with a serial port: if more than 
> one process gets access to it, data is stolen.
Okay, then lets choose your suggestion.

> 
> >>From my point of view it would be great to fix this bug without such an limitation.
> 
> I disagree, it is not a limitation! It is like a normal char device work.
> 
> What we have to test now is if your initial goal has been addressed! That is, in 
> an application that has more to do than just dealing with one PPS device, we can 
> use poll()/select() in order to avoid using threads.
I will do the final test.
I expect that it works with your patch.

Shall I prepare the patch?
Shall I add you as Co-author?
Or do you want to send your patch with me in reported-by and tested-by?

Fixes: eae9d2ba0cfc ("LinuxPPS: core support")?

CC stable?

Regards, Denis

> 
> Ciao,
> 
> Rodolfo
> 
> -- 
> GNU/Linux Solutions                  e-mail: giometti@...eenne.com
> Linux Device Driver                          giometti@...ux.it
> Embedded Systems                     phone:  +39 349 2432127
> UNIX programming
>

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