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Subject: Re: [PATCH 1/3] firmware: arm_sdei: fix possible deadlock
To:     James Morse <james.morse@arm.com>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <1577110975-54782-1-git-send-email-zhangliguang@linux.alibaba.com>
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Date:   Thu, 16 Jan 2020 09:54:10 +0800
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Hi James,

Sorry for the late reply, this problem was found by code review.


Thanks,

luanshi

?? 2019/12/23 22:22, luanshi д??:
> From: Liguang Zhang <zhangliguang@linux.alibaba.com>
>
> We call sdei_reregister_event() with sdei_list_lock held but
> _sdei_event_register() and sdei_event_destroy() also acquires
> sdei_list_lock thus creating A-A deadlock.
>
> Fixes: da351827240e ("firmware: arm_sdei: Add support for CPU and system power states")
> Signed-off-by: Liguang Zhang <zhangliguang@linux.alibaba.com>
> ---
>   drivers/firmware/arm_sdei.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
> index a479023..b122927 100644
> --- a/drivers/firmware/arm_sdei.c
> +++ b/drivers/firmware/arm_sdei.c
> @@ -651,20 +651,19 @@ static int sdei_reregister_event(struct sdei_event *event)
>   
>   	lockdep_assert_held(&sdei_events_lock);
>   
> -	err = _sdei_event_register(event);
> +	err = sdei_api_event_register(event->event_num,
> +				       sdei_entry_point,
> +				       event->registered,
> +				       SDEI_EVENT_REGISTER_RM_ANY, 0);
>   	if (err) {
>   		pr_err("Failed to re-register event %u\n", event->event_num);
> -		sdei_event_destroy(event);
> +		list_del(&event->list);
> +		kfree(event->registered);
>   		return err;
>   	}
>   
> -	if (event->reenable) {
> -		if (event->type == SDEI_EVENT_TYPE_SHARED)
> -			err = sdei_api_event_enable(event->event_num);
> -		else
> -			err = sdei_do_cross_call(_local_event_enable, event);
> -	}
> -
> +	if (event->reenable)
> +		err = sdei_api_event_enable(event->event_num);
>   	if (err)
>   		pr_err("Failed to re-enable event %u\n", event->event_num);
>