* Re: [staging-testing] drivers/staging/wfx/hif_tx.c
[not found] <CAGCTLNSwM+5kzSABDN7DGFKz4FcCN-DwUmhU8dzhtyW0=kh3gg@mail.gmail.com>
@ 2020-06-10 8:10 ` Jérôme Pouiller
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From: Jérôme Pouiller @ 2020-06-10 8:10 UTC (permalink / raw)
To: Greg Kroah-Hartman, devel, linux-kernel, Mohamed Dawod,
kernelnewbies
On Wednesday 10 June 2020 08:53:13 CEST Mohamed Dawod wrote:
> Hello,
>
> I read this point in staging/wfx/TODO file
>
> - In wfx_cmd_send(), "async" allow to send command without waiting the reply.
> It may help in some situation, but it is not yet used. In add, it may cause
> some trouble:
> https://lore.kernel.org/driverdev-devel/alpine.DEB.2.21.1910041317381.2992@hadrien/
> So, fix it (by replacing the mutex with a semaphore) or drop it.
>
> I think that this issue has already been fixed in hif_shutdown() function, hasn't it ?
Indeed, when I wrote the TODO file, the function hif_shutdown() didn't
exist yet.
> I have another question. How can (replacing the mutex with a semaphore) solve the problem?
My understanding is that a mutex aims to be acquired and released from the
same context. In some specific usages (RT-mutex? lock proving?), acquire
mutex from a context and release it from another can produce some errors.
In contrary a boolean semaphore does not have this restriction.
(can anyone confirm that?)
--
Jérôme Pouiller
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