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Mon, 24 Aug 2026 05:33:42 -0700 (PDT) Received: from dev-ag ([102.33.165.38]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6a59e1d741asm8342424a12.27.2026.08.24.05.33.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 05:33:41 -0700 (PDT) From: Andrew Gaylard To: Jakub Kicinski Cc: netdev@vger.kernel.org, wellslutw@gmail.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] net: sunplus: fix tx_poll spin_lock missing irqsave in NAPI context In-Reply-To: <20260822135103.6711ba25@kernel.org> (Jakub Kicinski's message of "Sat, 22 Aug 2026 13:51:03 -0700") References: <20260820130159.1584806-1-ag@ffroot.co.za> <20260822135103.6711ba25@kernel.org> User-Agent: mu4e 1.12.14; emacs 30.2 Date: Mon, 24 Aug 2026 14:33:36 +0200 Message-ID: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Jakub Kicinski writes: > On Thu, 20 Aug 2026 15:01:59 +0200 Andrew Gaylard wrote: >> spl2sw_tx_poll() runs in NAPI (softirq) context and acquires >> comm->tx_lock with plain spin_lock(). The hardirq handler >> spl2sw_ethernet_interrupt() acquires the same lock, so a hardirq on >> the same CPU while the NAPI poll holds the lock would deadlock with >> IRQs disabled. Use spin_lock_irqsave/spin_unlock_irqrestore. > > Please explain how the issue was found and how the fix was tested. > I mean - this is an ancient driver, if you don't have a way to test the > fix you should not be sending the patch. I'm testing on a Tibbo LTTP3G2 board: https://tibbo.com/store/tps/ltpp3g2.html This work is part of getting it to boot, getting it stable, adding a couple of missing drivers, and sending the changes upstream. I found the issue using lockdep. At least, I though I did, but I've not been able to reproduce it, so I must have been mistaken. Apologies. Please drop this patch. -- Andrew