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

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Message-ID: <132cbd87-cd5e-4e7e-a966-42c6232b88be@xsightlabs.com>
Date: Thu, 13 Mar 2025 11:07:25 -0400
From: Robbie King <robbiek@...ghtlabs.com>
To: Sudeep Holla <sudeep.holla@....com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Jassi Brar <jassisinghbrar@...il.com>, Huisong Li <lihuisong@...wei.com>,
 Adam Young <admiyo@...amperecomputing.com>
Subject: Re: [PATCH v2 01/13] mailbox: pcc: Fix the possible race in updation
 of chan_in_use flag

On 3/5/2025 11:38 AM, Sudeep Holla wrote:
> 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>

Tested-by: Robbie King <robbiek@...ghtlabs.com>