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[83.28.93.145]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b9b7ae52032sm113342366b.20.2026.03.28.14.22.24 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sat, 28 Mar 2026 14:22:25 -0700 (PDT) Date: Sat, 28 Mar 2026 22:22:17 +0100 From: Michal Pecio To: Alan Stern Cc: Thinh Nguyen , Oliver Neukum , =?UTF-8?B?QmrDuHJu?= Mork , USB list Subject: Re: correctly handling EPROTO Message-ID: <20260328222217.297200bd.michal.pecio@gmail.com> In-Reply-To: References: <4ada5d68-56f1-41b7-82d9-463901c927db@rowland.harvard.edu> <8a14fe29-0d92-4ce5-a7e2-2c084c710727@suse.com> <20260318223851.1f6d07d7.michal.pecio@gmail.com> <20260318235920.ioek26hdr25rkksp@synopsys.com> <1eaf4cf3-4278-4d04-87aa-8b6069d544e1@rowland.harvard.edu> <20260319231620.3ukqxsrwqikp5zbd@synopsys.com> <2929d47c-fc02-49d2-873e-758f24c43071@rowland.harvard.edu> <20260321021439.7pmcdrpb5oxbivct@synopsys.com> <20260321065424.76a80508.michal.pecio@gmail.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 21 Mar 2026 11:58:53 -0400, Alan Stern wrote: > On Sat, Mar 21, 2026 at 06:54:24AM +0100, Michal Pecio wrote: > > Nope, for many years now, if not forever, xhci-hcd has been > > restarting the endpoint after giving back the failed URB if its > > completion hasn't unlinked all remaining URBs. > > How can that work in the presence of BH givebacks? Certainly not reliably and I started a similar thread two years ago after coming to this exact realization. Does anyone know class drivers affected by this which could be used to validate such changes? Writing a patch is one thing, knowing whether it does any good is another. I recall that last time Mathias tried to touch this logic it caused a regression by unearthing more issues. I was reluctant to touch this mess in absence of known impact. The race is as old as BH giveback (2019) and automatic restarting is even older. It could get awkward if users (or driver developers) learned to expect this behavior. But if somebody can point out serious issues like data loss in storage then it's a different ball game. Regards, Michal