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 BE2A923184A; Mon, 24 Nov 2025 09:11:07 +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=1763975467; cv=none; b=K3iqrTEgVOp82+NqSrQLQTzlEZYK13eiDpDXGkmzQM1ky0gqvE9O8r8Szusv5+bBi4d0Hf+VxyivnSE2CDnl7Be9E7TovbyP30NeGzAqpbep6HIkEIziJkM78O96i4MNSvS5Z/bbfPCfbtHW//F3y60L6C/uTJbQvasS9lPYAi0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763975467; c=relaxed/simple; bh=h3g4JxPmkSuzn4A+hRY+XWm3wVyIpSZX3Sy+tuWzeq8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gS6iT77BlJ/KtOTcXxFP7Unx8ucoSUxmLOX6aaygSXwWTnKGgCm58rGEY/FO3R2EjNuK3EWyIbMeFtSNczhW2cfeNunIfonhsJQ+e4EskGG92mTDm+h8piwk3GL/ax24fUAQ5nSbd1bR3w2XkgqT7lCWAFBI4j66XsRPwlZKo1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LVkteaxM; 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="LVkteaxM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1531FC4CEF1; Mon, 24 Nov 2025 09:11:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763975467; bh=h3g4JxPmkSuzn4A+hRY+XWm3wVyIpSZX3Sy+tuWzeq8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=LVkteaxMddX1M3aC0bEsLu2/1lTKkED0KlkuA1s2zE6iuTreTG8vZt0FBYp0N2k/V 5Vj54xI6VQFpZ9u9voQPuctK9Ao+GrKD/+4O+c0ObWLrGZ0NhirnhOGqHujK4i8VOT aRtG7cGdzl4bCnl0kDA65ePANeMZJt4gL2VhpCjvtFsEOMRMv3/7lfzi7ZKB8FJHFh NFFCMPxr+amRLOchiWuNBT1Ykl1gZ/h8t7u22XR47X/mGudytA68lN0HEfEgp1+L+2 y6m5A/Oq2RmtPK9iZdrd+w+F7SdOtMeLV4zVTNwnlYQLmZXckTJV8t7e1WsbBlTkX3 CGSNnxT+iVuDA== Message-ID: Date: Mon, 24 Nov 2025 10:11:04 +0100 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] xhci: dbgtty: fix device unregister To: Mathias Nyman , =?UTF-8?Q?=C5=81ukasz_Bartosik?= , Mathias Nyman , Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, stable@vger.kernel.org References: <20251119212910.1245694-1-ukaszb@google.com> <2f05eedd-f152-4a4a-bf6c-09ca1ab7da40@kernel.org> <6171754f-1b84-47e0-a4da-0d045ea7546e@linux.intel.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 24. 11. 25, 8:48, Mathias Nyman wrote: > On 11/24/25 08:42, Jiri Slaby wrote: >> Hmm, CCing TTY MAINTAINERS entry would not hurt. >> >> On 19. 11. 25, 22:29, Łukasz Bartosik wrote: >>> From: Łukasz Bartosik >>> >>> When DbC is disconnected then xhci_dbc_tty_unregister_device() >>> is called. However if there is any user space process blocked >>> on write to DbC terminal device then it will never be signalled >>> and thus stay blocked indifinitely. >> >> indefinitely >> >>> This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device(). >>> The tty_vhangup() wakes up any blocked writers and causes subsequent >>> write attempts to DbC terminal device to fail. >>> >>> Cc: stable@vger.kernel.org >>> Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver") >>> Signed-off-by: Łukasz Bartosik >>> --- >>> Changes in v2: >>> - Replaced tty_hangup() with tty_vhangup() >> >> Why exactly? > > I recommended using tty_vhangup(), well actually tty_port_tty_vhangup() > to solve > issue '2' you pointed out. > To me it looks like tty_vhangup() is synchronous so it won't schedule > hangup work > and should be safe to call right before we destroy the port. Oops, right, my cscope DB was old and lead me to tty_hangup() instead (that schedules). >> 2) you schedule a tty hangup work and destroy the port right after: >>>       tty_unregister_device(dbc_tty_driver, port->minor); >>>       xhci_dbc_tty_exit_port(port); >>>       port->registered = false; >> You should to elaborate how this is supposed to work? > > Does tty_port_tty_vhangup() work here? it > 1. checks if tty is NULL > 2. is synchronous and should be safe to call before tty_unregister_device() Yes, this works for me. thanks, -- js suse labs