linux-kernel - Re: [PATCH v2 1/2] soc: fsl: qbman: Always disable interrupts when taking cgr

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Message-ID: <7bd6967a-7f0b-575f-d972-3bf98fab5a6a@seco.com>
Date:   Mon, 3 Apr 2023 11:22:12 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     Li Yang <leoyang.li@....com>, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org,
        Scott Wood <oss@...error.net>,
        Camelia Groza <camelia.groza@....com>,
        linux-kernel@...r.kernel.org, Roy Pledge <roy.pledge@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: Re: [PATCH v2 1/2] soc: fsl: qbman: Always disable interrupts when
 taking cgr_lock

On 4/3/23 10:02, Vladimir Oltean wrote:
> On Fri, Mar 31, 2023 at 11:14:12AM -0400, Sean Anderson wrote:
>> smp_call_function_single disables IRQs when executing the callback. To
>> prevent deadlocks, we must disable IRQs when taking cgr_lock elsewhere.
>> This is already done by qman_update_cgr and qman_delete_cgr; fix the
>> other lockers.
>> 
>> Fixes: c535e923bb97 ("soc/fsl: Introduce DPAA 1.x QMan device driver")
> 
> If you've identified smp_call_function_single() as the problem, then the
> true issue seems to lie in commit 96f413f47677 ("soc/fsl/qbman: fix
> issue in qman_delete_cgr_safe()") and not in the initial commit, no?

Yes, that seems better. I did a blame and saw that qman_delete_cgr_safe
had been around since the initial driver, but I didn't realize it worked
in a different way back then.

--Sean

> Anyway,
> 
> Tested-by: Vladimir Oltean <vladimir.oltean@....com>