linux-kernel - Re: [PATCH] soc: xilinx: Fix for call trace due to the usage of smp_processor

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Message-ID: <ae327757-11e2-44a8-8711-dcde7bdedffc@amd.com>
Date:   Wed, 15 Nov 2023 15:03:19 +0100
From:   Michal Simek <michal.simek@....com>
To:     Jay Buddhabhatti <jay.buddhabhatti@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc: xilinx: Fix for call trace due to the usage of
 smp_processor_id()



On 10/27/23 07:56, Jay Buddhabhatti wrote:
> From: HariBabu Gattem <haribabu.gattem@...inx.com>
> 
> When preemption is enabled in kernel and if any task which can be
> preempted should not use smp_processor_id() directly, since CPU
> switch can happen at any time, the previous value of cpu_id
> differs with current cpu_id. As a result we see the below call trace
> during xlnx_event_manager_probe.
> 
> [ 6.140197] dump_backtrace+0x0/0x190
> [ 6.143884] show_stack+0x18/0x40
> [ 6.147220] dump_stack_lvl+0x7c/0xa0
> [ 6.150907] dump_stack+0x18/0x34
> [ 6.154241] check_preemption_disabled+0x124/0x134
> [ 6.159068] debug_smp_processor_id+0x20/0x2c
> [ 6.163453] xlnx_event_manager_probe+0x48/0x250
> 
> To protect cpu_id, It is recommended to use get_cpu()/put_cpu()
> to disable preemption, get the cpu_id and enable preemption respectively.
> (For Reference, Documentation/locking/preempt-locking.rst and
> Documentation/kernel-hacking/hacking.rst)
> 
> Use preempt_disable()/smp_processor_id()/preempt_enable()
> API's to achieve the same.
> 
> Signed-off-by: HariBabu Gattem <haribabu.gattem@...inx.com>
> Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@....com>
> ---
>   drivers/soc/xilinx/xlnx_event_manager.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/xilinx/xlnx_event_manager.c b/drivers/soc/xilinx/xlnx_event_manager.c
> index 86a048a10a13..edfb1d5c10c6 100644
> --- a/drivers/soc/xilinx/xlnx_event_manager.c
> +++ b/drivers/soc/xilinx/xlnx_event_manager.c
> @@ -555,7 +555,7 @@ static void xlnx_disable_percpu_irq(void *data)
>   static int xlnx_event_init_sgi(struct platform_device *pdev)
>   {
>   	int ret = 0;
> -	int cpu = smp_processor_id();
> +	int cpu;
>   	/*
>   	 * IRQ related structures are used for the following:
>   	 * for each SGI interrupt ensure its mapped by GIC IRQ domain
> @@ -592,9 +592,12 @@ static int xlnx_event_init_sgi(struct platform_device *pdev)
>   	sgi_fwspec.param[0] = sgi_num;
>   	virq_sgi = irq_create_fwspec_mapping(&sgi_fwspec);
>   
> +	cpu = get_cpu();
>   	per_cpu(cpu_number1, cpu) = cpu;
>   	ret = request_percpu_irq(virq_sgi, xlnx_event_handler, "xlnx_event_mgmt",
>   				 &cpu_number1);
> +	put_cpu();
> +
>   	WARN_ON(ret);
>   	if (ret) {
>   		irq_dispose_mapping(virq_sgi);

Applied.
M