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([2001:a61:134a:e01:4312:e944:2d81:13bd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-485885c5bbdsm32167817f8f.36.2026.09.07.23.54.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Sep 2026 23:54:37 -0700 (PDT) Message-ID: Date: Tue, 8 Sep 2026 08:54:36 +0200 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] USB: cdc-acm: fix racy TIOCMIWAIT implementation To: Johan Hovold , Oliver Neukum Cc: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260907065501.101013-1-johan@kernel.org> <72615ee3-46eb-4639-a408-ba29c1235d08@suse.com> Content-Language: en-US From: Oliver Neukum In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 07.09.26 15:03, Johan Hovold wrote: > On Mon, Sep 07, 2026 at 02:46:16PM +0200, Oliver Neukum wrote: >> >> We could do that and it would indeed be simpler. >> >> But it would change the semantics so that past status changes >> no longer show up in TIOCMIWAIT. Is that really a good idea? > > Yes, as the current behaviour is both non-standard and inconsistent. > > If you have multiple tasks waiting waiting on status change, then only > one of them will detect it, for example. > > And if there are multiple changes (before or during TIOCMIWAIT) events > may be lost too. Very well. Ample reasons. Do you have a patch or do you want me to fix it? Regards Oliver