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[73.222.201.58]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b855af7806sm8719678eec.10.2026.02.09.18.58.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Feb 2026 18:58:37 -0800 (PST) Date: Mon, 9 Feb 2026 18:58:35 -0800 From: Joe Damato To: Thomas Gleixner Cc: intel-wired-lan@lists.osuosl.org, Tony Nguyen , Przemek Kitszel , netdev@vger.kernel.org Subject: Re: i40e: Fix preempt count leak in napi poll tracepoint Message-ID: Mail-Followup-To: Joe Damato , Thomas Gleixner , intel-wired-lan@lists.osuosl.org, Tony Nguyen , Przemek Kitszel , netdev@vger.kernel.org References: <87v7g8zv2o.ffs@tglx> <87a4xhbk6a.ffs@tglx> <877bslbg2g.ffs@tglx> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <877bslbg2g.ffs@tglx> On Tue, Feb 10, 2026 at 01:25:11AM +0100, Thomas Gleixner wrote: > On Mon, Feb 09 2026 at 23:56, Thomas Gleixner wrote: > > On Mon, Feb 09 2026 at 14:07, Joe Damato wrote: > > > >> On Sat, Feb 07, 2026 at 11:50:23AM +0100, Thomas Gleixner wrote: > >>> Using get_cpu() in the tracepoint assignment causes an obvious preempt > >>> count leak because nothing invokes put_cpu() to undo it: > >>> > >>> softirq: huh, entered softirq 3 NET_RX with preempt_count 00000100, exited with 00000101? > >>> > >>> This clearly has seen a lot of testing in the last 3+ years... > >> > >> I'm the author who introduced the bug. FWIW, I did use it quite a bit when I > >> had i40e devices. > > > > Right, but always with PREEMPT_NONE and no debug option which would > > enforce PREEMPT_COUNT ... > > Forgot to mention that's what is required before submitting patches > according to Documentation/process/submit-checklist.rst This is a very helpful reply, thanks! > But who cares about documentation aside of the people who write it? I've written a lot of documentation, too, but sometimes people just make mistakes. - Joe