From: Peng Zhang <zhangpeng.00@bytedance.com>
To: gregkh@linuxfoundation.org, jirislaby@kernel.org,
ilpo.jarvinen@linux.intel.com
Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
songmuchun@bytedance.com, Peng Zhang <zhangpeng.00@bytedance.com>,
stable@vger.kernel.org
Subject: [PATCH v2] serial: 8250: always disable IRQ during THRE test
Date: Thu, 16 Oct 2025 15:05:16 +0800 [thread overview]
Message-ID: <20251016070516.37549-1-zhangpeng.00@bytedance.com> (raw)
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>
---
drivers/tty/serial/8250/8250_port.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 719faf92aa8a..f1740cc91143 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2147,8 +2147,7 @@ static void serial8250_THRE_test(struct uart_port *port)
if (up->port.flags & UPF_NO_THRE_TEST)
return;
- if (port->irqflags & IRQF_SHARED)
- disable_irq_nosync(port->irq);
+ disable_irq(port->irq);
/*
* Test for UARTs that do not reassert THRE when the transmitter is idle and the interrupt
@@ -2170,8 +2169,7 @@ static void serial8250_THRE_test(struct uart_port *port)
serial_port_out(port, UART_IER, 0);
}
- if (port->irqflags & IRQF_SHARED)
- enable_irq(port->irq);
+ enable_irq(port->irq);
/*
* If the interrupt is not reasserted, or we otherwise don't trust the iir, setup a timer to
--
2.20.1
next reply other threads:[~2025-10-16 7:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-16 7:05 Peng Zhang [this message]
2025-10-16 8:55 ` [PATCH v2] serial: 8250: always disable IRQ during THRE test Muchun Song
2025-10-22 9:57 ` Greg KH
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20251016070516.37549-1-zhangpeng.00@bytedance.com \
--to=zhangpeng.00@bytedance.com \
--cc=gregkh@linuxfoundation.org \
--cc=ilpo.jarvinen@linux.intel.com \
--cc=jirislaby@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=songmuchun@bytedance.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox