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Subject: Re: [PATCH RESEND v2 2/5] extcon: extcon-max14577: Fix potential
 work-queue cancellation race
To:     Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        Matti Vaittinen <mazziesaccount@gmail.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        linux-kernel@vger.kernel.org
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
Message-ID: <e9e46963-29ed-0358-1f2c-926c3a40686e@samsung.com>
Date:   Thu, 10 Jun 2021 18:41:19 +0900
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References: <cover.1623146580.git.matti.vaittinen@fi.rohmeurope.com>
        <CGME20210608101006epcas1p3955e119400f64e4f7f30ea17c8b957c0@epcas1p3.samsung.com>
        <ee8545f59ae3a93f0a70f640ecbd7e31cfadbcb9.1623146580.git.matti.vaittinen@fi.rohmeurope.com>
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On 6/8/21 7:09 PM, Matti Vaittinen wrote:
> The extcon IRQ schedules a work item. IRQ is requested using devm while
> WQ is cancelld at remove(). This mixing of devm and manual unwinding has
> potential case where the WQ has been emptied (.remove() was ran) but
> devm unwinding of IRQ was not yet done. It is possible the IRQ is triggered
> at this point scheduling new work item to the already flushed queue.
> 
> Use new devm_work_autocancel() to remove the remove() and to kill the bug.
> 
> Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
> ---
> 
> Please note that the change is compile-tested only. All proper testing is
> highly appreciated.
> ---
>  drivers/extcon/extcon-max14577.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/extcon/extcon-max14577.c b/drivers/extcon/extcon-max14577.c
> index ace523924e58..5476f48ed74b 100644
> --- a/drivers/extcon/extcon-max14577.c
> +++ b/drivers/extcon/extcon-max14577.c
> @@ -6,6 +6,7 @@
>  // Chanwoo Choi <cw00.choi@samsung.com>
>  // Krzysztof Kozlowski <krzk@kernel.org>
>  
> +#include <linux/devm-helpers.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/i2c.h>
> @@ -673,7 +674,10 @@ static int max14577_muic_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, info);
>  	mutex_init(&info->mutex);
>  
> -	INIT_WORK(&info->irq_work, max14577_muic_irq_work);
> +	ret = devm_work_autocancel(&pdev->dev, &info->irq_work,
> +				   max14577_muic_irq_work);
> +	if (ret)
> +		return ret;
>  
>  	switch (max14577->dev_type) {
>  	case MAXIM_DEVICE_TYPE_MAX77836:
> @@ -766,15 +770,6 @@ static int max14577_muic_probe(struct platform_device *pdev)
>  	return ret;
>  }
>  
> -static int max14577_muic_remove(struct platform_device *pdev)
> -{
> -	struct max14577_muic_info *info = platform_get_drvdata(pdev);
> -
> -	cancel_work_sync(&info->irq_work);
> -
> -	return 0;
> -}
> -
>  static const struct platform_device_id max14577_muic_id[] = {
>  	{ "max14577-muic", MAXIM_DEVICE_TYPE_MAX14577, },
>  	{ "max77836-muic", MAXIM_DEVICE_TYPE_MAX77836, },
> @@ -797,7 +792,6 @@ static struct platform_driver max14577_muic_driver = {
>  		.of_match_table = of_max14577_muic_dt_match,
>  	},
>  	.probe		= max14577_muic_probe,
> -	.remove		= max14577_muic_remove,
>  	.id_table	= max14577_muic_id,
>  };
>  
> 

Acked-by: Chanwoo Choi <cw00.choi@samsung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics