[PATCH v2 01/13] mailbox: pcc: Fix the possible race in updation of chan_in_use flag

Sudeep Holla
2025-03-05T16:39:00Z

From: Huisong Li <lihuisong@huawei.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@huawei.com>
(sudeep.holla: Minor updates to the subject and commit message)
Signed-off-by: Sudeep Holla <sudeep.holla@arm.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()
+ */
+ pchan->chan_in_use = false;
mbox_chan_received_data(chan, NULL);

check_and_ack(pchan, chan);
- pchan->chan_in_use = false;

return IRQ_HANDLED;
}

--
2.34.1