From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 DE25C3E47B; Thu, 16 Apr 2026 06:22:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776320530; cv=none; b=KMFmJ/wbr6VHa11DBik+8ZHT6fBAFhSpfF0kiznGknsHZQi8PsbAgrR8aOC3vPcilKzHN3ilnlikeCmzuRuO+n0h2fIfcI54ElY4FI1MBv6ODZkgmPkFbspPqb/EpX1LI9ZBeCDebnz+auhVeDe8H/YyGz69gTYRxjoEWNSzRjk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776320530; c=relaxed/simple; bh=L03K7wgv0HG3lp+inFLDMx7vtTcPsOMgCaTopreSxt8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WzCjWbzm9dWXwtkLF2+AOMC5Smuzws0iysUIR71lc8Ctu+xf++AjKBT6WsGU5eY3u/z9cV8JEFKh93oMHkFwdqwZfZaKJSH8Omz1EB8I3FCH+k8JA7lq2pQJ5uqPJFXUu0bdoMGeQDlmjCWQfPX0FbmGMLmJbVQ6mBc4b6hY4Ks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=JGlQOhpC; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=DYCNXtQa; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="JGlQOhpC"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="DYCNXtQa" Date: Thu, 16 Apr 2026 08:21:59 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1776320520; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=L03K7wgv0HG3lp+inFLDMx7vtTcPsOMgCaTopreSxt8=; b=JGlQOhpCttHrTVGoh/Gin7OP8xVbnJaZ1oa0t6/Ob6aAUCHkGmfPDsDcqUy7GdW8tiX164 ChpFaKfFqd3iPIKHvPNZqcv7bOYnzTmubn6QvPkhVnNigsNnvIN3RvUnYAu9AK6B6IlocY I829e9tkcSA8oSDuMBeBfSXU9gxeY5uHMMLU6wQ7WvgSoNbcoTdnYjD9M6xioW/gM3c3+P XHRhKPGozlxtCiTz3T4wdBzaRVDGdqQ3SfhN19kq8kGmG7AUBIEe2Tk0haryeIba/TDEWo lBOkgjanZWmBJzxFdnN1+YXSB1s9/sqRhLYvFy3T6QVqLbIbUEOY+cg3xIrCqg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1776320520; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=L03K7wgv0HG3lp+inFLDMx7vtTcPsOMgCaTopreSxt8=; b=DYCNXtQaJi3GaDQgG8vnwfptTcyYwoS89pEjawunYcmF2OUGGXhIAQU196GqugZlqe8Pgl VXHAebvshabDOqBg== From: Sebastian Andrzej Siewior To: Marek Vasut Cc: netdev@vger.kernel.org, stable@vger.kernel.org, "David S. Miller" , Andrew Lunn , Eric Dumazet , Jakub Kicinski , Nicolai Buchwitz , Paolo Abeni , Ronald Wahl , Yicong Hui , linux-kernel@vger.kernel.org Subject: Re: [net,PATCH v3 1/2] net: ks8851: Reinstate disabling of BHs around IRQ handler Message-ID: <20260416062159.fPxqc52X@linutronix.de> References: <20260414103327.113500-1-marex@nabladev.com> <20260414125753.Im6GAIHn@linutronix.de> <2fcfb84f-69f6-493e-94d6-95d85d8000f6@nabladev.com> <20260414145218.lsNpdAJI@linutronix.de> <7734527a-d08b-49fa-b258-c37c5ae2da55@nabladev.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7734527a-d08b-49fa-b258-c37c5ae2da55@nabladev.com> On 2026-04-16 01:14:35 [+0200], Marek Vasut wrote: > > spin_unlock_bh(&ks->statelock)? After that unlock, the softirq must be > > processed and __netdev_alloc_skb() _could_ observe pending softirqs but > > not from ks8851. > Because __netdev_alloc_skb() also enables/disables BH , see the "else" Yes. But there is no softirq raised in that part. That softirq is raised by netif_wake_queue() within a bh disabled section. Therefore upon the unlock the softirq must be invoked. After that, rhe allocation later on may invoke softirqs which were raised but I don't see how ks8851 can be part of it. Before commit 0913ec336a6c0 ("net: ks8851: Fix deadlock with the SPI chip variant") there was no _bh around it meaning the softirq was raised but not invoked immediately. This happened on the bh unlock during memory allocation. Therefore I am saying this backtrace is from an older kernel. If there is a flaw in my the theory please explain _how_ you managed that get that backtrace. I am sure it must have from an older kernel and _now_ this lockup also happens on !RT kernels (except for the SPI platform). Sebastian