linux-kernel - Re: drivers/misc/habanalabs: atomic

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Message-ID: <CAFCwf11Fg8gH6wMO5aPqwtNovgB153J2vNWdLF_zrua5b6Qetw@mail.gmail.com>
Date:   Wed, 23 Sep 2020 11:41:50 +0300
From:   Oded Gabbay <oded.gabbay@...il.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ofir Bitton <obitton@...ana.ai>,
        Lee Jones <lee.jones@...aro.org>,
        Omer Shpigelman <oshpigelman@...ana.ai>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: drivers/misc/habanalabs: atomic_t api usage inconsistencies

On Tue, Sep 22, 2020 at 1:08 AM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> All,
>
> While I was looking at the atomic_t api usages for an unrelated issue,
> I noticed free_slots_cnt in struct hl_cq incerment/decrement/reads are
> not consistent.
>
> atomic_inc() and atomic_set() are used, however instead of atomic_read()
> the value is referenced directly in
> drivers/misc/habanalabs/common/hw_queue.c
>
> hl_queue_add_ptr()
> atomic_t *free_slots = &hdev->completion_queue[q->cq_id].free_slots_cnt;
>
> hl_hw_queue_schedule_cs()
>
> atomic_t *free_slots = &hdev->completion_queue[i].free_slots_cnt;
>
> Any reason why this is necessary. I don't know that this is causing
> any problems, it is just odd that access is inconsistent.
>
> thanks,
> -- Shuah

Hi Shuah,
Thanks for taking notice of this issue :)
We will take a deeper look and fix the inconsistencies, although I
must say that we didn't notice any impact of this issue.
Thanks again.
Oded