From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0010432F771; Wed, 15 Oct 2025 15:49:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760543379; cv=none; b=bLOcYMJwRrrz90uAH8XTYcIYfUYrcI7WN8tIHJ3MIoVu/GjT1EB9i/XHKfYlWuInN49xKBBr8x4fQSTtUAZSMmJCjEuhqJWVzmK8l/p6qWXwU0Be5hEGve3uiNNNIkSkDDCDWF68Ia1d7r4fii24zJjIdqGB+ovIb9fWE95htTM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760543379; c=relaxed/simple; bh=SvJQkrxK8S2FzNYqFRInIPoqJAGTOO1/f98SdCFBCtE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=J/6RZif0+BHyE+MTmB6seGK3Ix5t0pb9BbK8ziSDeQGJyVuECa6KF65VhDwiQL2T6Ykk6tDfIiOvzaAPL7XkJ7TH/doG8j0yK7FWRuIPkKSYz2O1sHEPh1u06yQPu7dGsJu0+tUZwNjhokCHB5MpOCAYXyM0+f4oGQUqIzHvez4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ttyfpz0d; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ttyfpz0d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39411C4CEF8; Wed, 15 Oct 2025 15:49:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760543378; bh=SvJQkrxK8S2FzNYqFRInIPoqJAGTOO1/f98SdCFBCtE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ttyfpz0d22MFc/WgqeuQ8VFQn6uGy9JK9dsvqaD3esJ6yrCwGhnD6IIa3LdZu22jE td5ZqWtRx+nBq30Q5ihELYPpQCO03WatZ+NIQ1Qc/52pOY5ZBMLmMoHrSrRo6Kgoq9 2k82RaLJoAaQSCjdD90QX9GAZfCc12No1us3ylGTCTN3wUupOjY42X2G5PhplZbJ8H 2fmWV860hNDNJjyXp83gNbDV2KcpKmOwSSvtyIA27EuLmxj+hu1KQllN2NcL7pkjDk Mtpf1ciOvbkJWhVAXrsONBa0hFyn9DYe/1IEybzb6MojkaaedNJZARErJHvS0ykjDs y4Daadk2JiIlQ== Message-ID: <0eb4c357-aafd-42bd-a4fd-687a91831bf4@kernel.org> Date: Wed, 15 Oct 2025 17:49:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] serial: 8250: always disable IRQ during THRE test To: Peng Zhang , gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, songmuchun@bytedance.com, =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , buytenh@arista.com, Andy Shevchenko References: <20251014114727.1186-1-zhangpeng.00@bytedance.com> <94d19d6d-5bb5-4156-8499-0be3d227f478@bytedance.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 14. 10. 25, 14:19, Peng Zhang wrote: > > > 在 2025/10/14 19:47, Peng Zhang 写道: >> 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. >> >> Fixes: 039d4926379b ("serial: 8250: Toggle IER bits on only after irq >> has been set up") >> Signed-off-by: Peng Zhang >> --- >>   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..addeef7a0d59 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_nosync(port->irq); > disable_irq_nosync() may need to be changed to disable_irq() to prevent > interrupts that are currently being handled. Make sense to me. Care to Cc the people from 039d4926379b next time, so that they can comment? >>       /* >>        * 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 > -- js suse labs