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Tue, 10 Feb 2026 00:25:17 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id uCplfnqdpG3p for ; Tue, 10 Feb 2026 00:25:16 +0000 (UTC) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=172.234.252.31; helo=sea.source.kernel.org; envelope-from=tglx@kernel.org; receiver= DMARC-Filter: OpenDMARC Filter v1.4.2 smtp1.osuosl.org 6F644812B9 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org 6F644812B9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by smtp1.osuosl.org (Postfix) with ESMTPS id 6F644812B9 for ; Tue, 10 Feb 2026 00:25:16 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id A3A8443AD7; Tue, 10 Feb 2026 00:25:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D640C116C6; Tue, 10 Feb 2026 00:25:14 +0000 (UTC) From: Thomas Gleixner To: Joe Damato Cc: intel-wired-lan@lists.osuosl.org, Tony Nguyen , Przemek Kitszel , netdev@vger.kernel.org In-Reply-To: <87a4xhbk6a.ffs@tglx> References: <87v7g8zv2o.ffs@tglx> <87a4xhbk6a.ffs@tglx> Date: Tue, 10 Feb 2026 01:25:11 +0100 Message-ID: <877bslbg2g.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770683115; bh=Wpfw2uqDmLqrlx715dbScHeqTNO7aVvos/5uQh5ZKms=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=ra5OCJdnfuCdFx6NO89ZSB9V2hj4VPkmFrvDZNdgGByBa5dfNQVHsoqLer8O2UTOv X8zibP/PJ+MGMwrDXOs+srb/xtNvrxbY+ZVHdWSx1oR7HH8caBZ3OgALUkd14Bh6zX pELM7Irep/kNcgWelpHebQ5VTTSv5PHSlrGU15w5YbFJhiH827vVZa/zPcCJy3mMvD NM/g0rJFhA/L9jySY0X0iXDkINX3BXKNh0HwUX1P+w1C/drv/tZkShwco4Ilwm5egN LI4PJ8izbzekt15Zbss65v9puacrwVzng32haZrfnNNIJ4i30xPF8vSXHtR2KxxjBd gXdlTnjLgMniw== X-Mailman-Original-Authentication-Results: smtp1.osuosl.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org X-Mailman-Original-Authentication-Results: smtp1.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=ra5OCJdn Subject: Re: [Intel-wired-lan] i40e: Fix preempt count leak in napi poll tracepoint X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" 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 But who cares about documentation aside of the people who write it? Thanks, tglx 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 E805D1FCFFC for ; Tue, 10 Feb 2026 00:25:15 +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=1770683116; cv=none; b=T/Nw8vX3wUDaeDrIsREawwphyxPbcIxb9NkJCyPgm1WS+dd/ZvkwqobNczbd0FXhj1FHmIVmQWpIvkz9AdN3Jf5MspUHcsg0uso+sRbNIf8Ly63hWhWM1gUr/UT5x8WdSm2N5bIkp+tWLnFlU76FFPXfs9vBTqAkhTjrI84fP9s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770683116; c=relaxed/simple; bh=Wpfw2uqDmLqrlx715dbScHeqTNO7aVvos/5uQh5ZKms=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=NmDzo5qe3Up1XbyVm3Ebnd8xfev9WX6G4ZJUhU95h6puSCKWqTj5bpXgfUXOZ+Fo4w46bDVp0GQ8Pj6XNZzJmD1zsB5guh0tt2KChIZ/pgmjw9B7/0G18PLpxVTgmTHirQ+d/vodiv7ipUC4TJAinRS/HINs9FAvHT1DwtPa/3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ra5OCJdn; 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="ra5OCJdn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D640C116C6; Tue, 10 Feb 2026 00:25:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770683115; bh=Wpfw2uqDmLqrlx715dbScHeqTNO7aVvos/5uQh5ZKms=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=ra5OCJdnfuCdFx6NO89ZSB9V2hj4VPkmFrvDZNdgGByBa5dfNQVHsoqLer8O2UTOv X8zibP/PJ+MGMwrDXOs+srb/xtNvrxbY+ZVHdWSx1oR7HH8caBZ3OgALUkd14Bh6zX pELM7Irep/kNcgWelpHebQ5VTTSv5PHSlrGU15w5YbFJhiH827vVZa/zPcCJy3mMvD NM/g0rJFhA/L9jySY0X0iXDkINX3BXKNh0HwUX1P+w1C/drv/tZkShwco4Ilwm5egN LI4PJ8izbzekt15Zbss65v9puacrwVzng32haZrfnNNIJ4i30xPF8vSXHtR2KxxjBd gXdlTnjLgMniw== From: Thomas Gleixner To: Joe Damato 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 In-Reply-To: <87a4xhbk6a.ffs@tglx> References: <87v7g8zv2o.ffs@tglx> <87a4xhbk6a.ffs@tglx> Date: Tue, 10 Feb 2026 01:25:11 +0100 Message-ID: <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 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 But who cares about documentation aside of the people who write it? Thanks, tglx