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From:   Mike Leach <mike.leach@linaro.org>
Date:   Thu, 20 Aug 2020 09:12:12 +0100
Message-ID: <CAJ9a7VjCX1Gmw0b8rTK8extrc6_mmbRn2BRXNK-+sSN9_6BMtw@mail.gmail.com>
Subject: Re: [PATCH] coresight: cti: disclaim device only when it's claimed
To:     Tingwei Zhang <tingwei@codeaurora.org>
Cc:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        tsoni@codeaurora.org,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
        Mao Jinlong <jinlmao@codeaurora.org>,
        Coresight ML <coresight@lists.linaro.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, 18 Aug 2020 at 12:11, Tingwei Zhang <tingwei@codeaurora.org> wrote:
>
> Coresight_claim_device() is called in cti_starting_cpu() only
> when CTI is enabled while coresight_disclaim_device() is called
> uncontionally in cti_dying_cpu(). This triggered below WARNING.
> Only call disclaim device when CTI device is enabled to fix it.
>
> [   75.989643] WARNING: CPU: 1 PID: 14 at
> kernel/drivers/hwtracing/coresight/coresight.c:209
> coresight_disclaim_device_unlocked+0x10/0x24
> [   75.989697] CPU: 1 PID: 14 Comm: migration/1 Not tainted
> 5.9.0-rc1-gff1304be0a05-dirty #21
> [   75.989709] Hardware name: Thundercomm Dragonboard 845c (DT)
> [   75.989737] pstate: 80c00085 (Nzcv daIf +PAN +UAO BTYPE=--)
> [   75.989758] pc : coresight_disclaim_device_unlocked+0x10/0x24
> [   75.989775] lr : coresight_disclaim_device+0x24/0x38
> [   75.989783] sp : ffff800011cd3c90
> .
> [   75.990018] Call trace:
> [   75.990041]  coresight_disclaim_device_unlocked+0x10/0x24
> [   75.990066]  cti_dying_cpu+0x34/0x4c
> [   75.990101]  cpuhp_invoke_callback+0x84/0x1e0
> [   75.990121]  take_cpu_down+0x90/0xe0
> [   75.990154]  multi_cpu_stop+0x134/0x160
> [   75.990171]  cpu_stopper_thread+0xb0/0x13c
> [   75.990196]  smpboot_thread_fn+0x1c4/0x270
> [   75.990222]  kthread+0x128/0x154
> [   75.990251]  ret_from_fork+0x10/0x18
>
> Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver")
> Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
> ---
>  drivers/hwtracing/coresight/coresight-cti.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
> index 3ccc703dc940..d6fea6efec71 100644
> --- a/drivers/hwtracing/coresight/coresight-cti.c
> +++ b/drivers/hwtracing/coresight/coresight-cti.c
> @@ -742,7 +742,8 @@ static int cti_dying_cpu(unsigned int cpu)
>
>         spin_lock(&drvdata->spinlock);
>         drvdata->config.hw_powered = false;
> -       coresight_disclaim_device(drvdata->base);
> +       if (drvdata->config.hw_enabled)
> +               coresight_disclaim_device(drvdata->base);
>         spin_unlock(&drvdata->spinlock);
>         return 0;
>  }
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
Reviewed-by: Mike Leach <mike.leach@linaro.org>

-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK