Re: [PATCH v2] serial: 8250: always disable IRQ during THRE test

On Thu, Oct 16, 2025 at 3:05 PM Peng Zhang zhangpeng.00@bytedance.com wrote:

commit 039d4926379b ("serial: 8250: Toggle IER bits on only after irq has been set up") moved IRQ setup before the THRE test, so the interrupt handler can run during the test and race with its IIR reads. This can produce wrong THRE test results and cause spurious registration of the serial8250_backup_timeout timer. Unconditionally disable the IRQ for the short duration of the test and re-enable it afterwards to avoid the race.

Cc: stable@vger.kernel.org Fixes: 039d4926379b ("serial: 8250: Toggle IER bits on only after irq has been set up") Signed-off-by: Peng Zhang zhangpeng.00@bytedance.com

Reviewed-by: Muchun Song songmuchun@bytedance.com