* Re: Linux DVB frontend issue
2014-05-26 14:17 ` Linux DVB frontend issue Romain Baeriswyl
@ 2014-05-26 16:03 ` Mauro Carvalho Chehab
0 siblings, 0 replies; 2+ messages in thread
From: Mauro Carvalho Chehab @ 2014-05-26 16:03 UTC (permalink / raw)
To: Romain Baeriswyl; +Cc: Christian Ruppert, Ole Ernst, linux-media
Hi Romain,
Em Mon, 26 May 2014 16:17:48 +0200 (CEST)
Romain Baeriswyl <Romain.Baeriswyl@abilis.com> escreveu:
> Dear Mauro,
>
> We are using the Linux DVB frontend module on our platform and
> we are facing an issue when having concurrent calls with FE_SET_FRONTEND
> and FE_GET_FRONTEND ioctl.
>
> Issue is that both ioctls are using the same dtv_property_cache buffer.
> If a FE_SET_FRONTEND ioctl is interrupted by a FE_GET_FRONTEND then the
> dtv_property_cache is overwritten with the result of the FE_GET_FRONTEND.
> When the FE_SET_FRONTEND operation resumes, the dtv_property_cache may
> not be accurate anymore.
>
> Did you already face this issue?
No. Never tried to do it in practice, but I don't think it is even
possible to have two concurrent ioctl calls ATM, because there is a
semaphore at dvb_frontend_ioctl() preventing it.
> Up to now I tried, without success, to think on a fix that does not impact
> too much the existing code.
>
> One solution could be to have one cache for reading properties and one other
> cache for writing properties, but this will impact all the drivers below
> the DVB frontend.
>
> Do you see another less impacting solution?
Are you sure that the corruption you're seeing is not at userspace
sharing the same buffer for both ioctl's?
>
> Best regards,
>
> Romain Baeriswyl
>
> Abilis Systems
> 3, chemin Pré Fleuri
> CH-1228 Plan-Les-Ouates
> Geneva
>
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 2+ messages in thread