From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: "Alban Bedel" <alban.bedel@lht.dlh.de>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
"Nam Cao" <namcao@linutronix.de>,
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Lennert Buytenhek" <buytenh@arista.com>,
"Peng Zhang" <zhangpeng.00@bytedance.com>,
stable@vger.kernel.org, "Muchun Song" <songmuchun@bytedance.com>,
"Maximilian Lueer" <maximilian.lueer@lht.dlh.de>
Subject: Re: [PATCH v3] serial: 8250: always disable IRQ during THRE test
Date: Thu, 12 Feb 2026 12:15:50 +0200 [thread overview]
Message-ID: <aY2oVjCL21wL-8aE@smile.fi.intel.com> (raw)
In-Reply-To: <5964c41f-ddd3-406d-91b1-62fa33364163@kernel.org>
On Thu, Feb 12, 2026 at 09:41:08AM +0100, Jiri Slaby wrote:
> On 09. 02. 26, 12:32, Alban Bedel 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.
...
> > v2: Replaced disable_irq_nosync() with disable_irq() to prevent interrupts
> > that are currently being handled
>
> This made me to check, why/how this is possible. It appears to be, but only
> thanks to:
> 205d300aea75 serial: 8250: change lock order in serial8250_do_startup()
>
> And the change should be documented in the commit log. Especially to avoid
> stable backports to trees without 205d300aea75.
There is a de facto tag Depends-on: which might be used here.
--
With Best Regards,
Andy Shevchenko
prev parent reply other threads:[~2026-02-12 10:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 11:32 [PATCH v3] serial: 8250: always disable IRQ during THRE test Alban Bedel
2026-02-12 8:41 ` Jiri Slaby
2026-02-12 10:15 ` Andy Shevchenko [this message]
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