linux-kernel - Re: [PATCH v2 01/13] mailbox: pcc: Fix the possible race in updation of chan_in

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Message-ID: <4ecf3a7a-7a68-fd56-ed93-fbae82e2b0e3@huawei.com>
Date: Tue, 11 Mar 2025 19:40:53 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: Sudeep Holla <sudeep.holla@....com>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
CC: Jassi Brar <jassisinghbrar@...il.com>, Adam Young
	<admiyo@...amperecomputing.com>, Robbie King <robbiek@...ghtlabs.com>
Subject: Re: [PATCH v2 01/13] mailbox: pcc: Fix the possible race in updation
 of chan_in_use flag


在 2025/3/6 0:38, Sudeep Holla 写道:
> From: Huisong Li <lihuisong@...wei.com>
>
> The function mbox_chan_received_data() calls the Rx callback of the
> mailbox client driver. The callback might set chan_in_use flag from
> pcc_send_data(). This flag's status determines whether the PCC channel
> is in use.
>
> However, there is a potential race condition where chan_in_use is
> updated incorrectly due to concurrency between the interrupt handler
> (pcc_mbox_irq()) and the command sender(pcc_send_data()).
>
> The 'chan_in_use' flag of a channel is set to true after sending a
> command. And the flag of the new command may be cleared erroneous by
> the interrupt handler afer mbox_chan_received_data() returns,
>
> As a result, the interrupt being level triggered can't be cleared in
> pcc_mbox_irq() and it will be disabled after the number of handled times
> exceeds the specified value. The error log is as follows:
>
>    |  kunpeng_hccs HISI04B2:00: PCC command executed timeout!
>    |  kunpeng_hccs HISI04B2:00: get port link status info failed, ret = -110
>    |  irq 13: nobody cared (try booting with the "irqpoll" option)
>    |  Call trace:
>    |   dump_backtrace+0x0/0x210
>    |   show_stack+0x1c/0x2c
>    |   dump_stack+0xec/0x130
>    |   __report_bad_irq+0x50/0x190
>    |   note_interrupt+0x1e4/0x260
>    |   handle_irq_event+0x144/0x17c
>    |   handle_fasteoi_irq+0xd0/0x240
>    |   __handle_domain_irq+0x80/0xf0
>    |   gic_handle_irq+0x74/0x2d0
>    |   el1_irq+0xbc/0x140
>    |   mnt_clone_write+0x0/0x70
>    |   file_update_time+0xcc/0x160
>    |   fault_dirty_shared_page+0xe8/0x150
>    |   do_shared_fault+0x80/0x1d0
>    |   do_fault+0x118/0x1a4
>    |   handle_pte_fault+0x154/0x230
>    |   __handle_mm_fault+0x1ac/0x390
>    |   handle_mm_fault+0xf0/0x250
>    |   do_page_fault+0x184/0x454
>    |   do_translation_fault+0xac/0xd4
>    |   do_mem_abort+0x44/0xb4
>    |   el0_da+0x40/0x74
>    |   el0_sync_handler+0x60/0xb4
>    |   el0_sync+0x168/0x180
>    |  handlers:
>    |   pcc_mbox_irq
>    |  Disabling IRQ #13
>
> To solve this issue, pcc_mbox_irq() must clear 'chan_in_use' flag before
> the call to mbox_chan_received_data().
>
> Signed-off-by: Huisong Li <lihuisong@...wei.com>
> (sudeep.holla: Minor updates to the subject and commit message)
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>   drivers/mailbox/pcc.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 82102a4c5d68839170238540a6fed61afa5185a0..f2e4087281c70eeb5b9b33371596613a371dff4f 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -333,10 +333,15 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
>   	if (pcc_chan_reg_read_modify_write(&pchan->plat_irq_ack))
>   		return IRQ_NONE;
>   
> +	/*
> +	 * Clear this flag immediately after updating interrupt ack register
> +	 * to avoid possible race in updatation of the flag from
> +	 * pcc_send_data() that could execute from mbox_chan_received_data()
This comment may be inappropriate becuase of the moving of clearing 
interrupt ack register in patch 2/13.
I suggested that fix it in this patch or patch 2/13.
> +	 */
> +	pchan->chan_in_use = false;
>   	mbox_chan_received_data(chan, NULL);
>   
>   	check_and_ack(pchan, chan);
> -	pchan->chan_in_use = false;
>   
>   	return IRQ_HANDLED;
>   }
>