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 E3DB9306D2A for ; Mon, 16 Feb 2026 15:37:48 +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=1771256270; cv=none; b=QY2O0W1+bZvlXG4T435vH4RT+O5SmKUap5EPHoH82uhqFBmCmYX7ntvfsegdOTZ1RKot4DxI6aHh+xvNmrcCxoGXDf+2cUAj3tMHFco9IbImpqQ4cWvzEmI4BHJe/UjReDzTQXQsnArYU5wAaipE7emA3Vbhg9LxaLQYw/VgcHU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771256270; c=relaxed/simple; bh=4bDUvi6EEPic+v6Ow+64yXCVquOAAgfRnQCiCWcMckU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BRlE1aYs4kAehacex83gjkrK7LZkMyGeDhAvAL0D136WaZrWkJZdRJG6mk08aLF52+zNvuZypZQZRkQegaZmKgvutOypQnAu2sxJz5q3m893roOikXVU5Ay92xH2BZoFbRVHIwtAor8hlXQrcnUj3ledjjIFeMUxPdDZfYWkY+Y= 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=hJkGpQ3w; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=sv9xFOQP; 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="hJkGpQ3w"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="sv9xFOQP" Date: Mon, 16 Feb 2026 16:37:45 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1771256267; 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=6PnG3DeeB6mHo0hnnLDiezB/8Zfvc61iiF9yoYDdbs0=; b=hJkGpQ3wBA/LVJYeFutd1Ooe4HXfnZ3K7a+xdXAssA9CfQuL+SefTFp4oRLwEqgQKvblqC JoNTJol/AkcSPZG1qLoTrDnssecG6Wc0UY6Cj0G1hWMLPss/qc4R/72ypC2GEMDii/P7k8 QGvWVVXZwKwcRtoWVmrSil7ueFOKWdSkbjgyi/XPv0Td+ut5kQYyago+xZA7qEwV0Z4doi OisvBjeL8ocvDWxJBukYUX4Nn6dwgilXRcJ5TwmyvZiXRv+Ohg1FXVoecNMYg8M2ro/Sbs fPl/0xV/c1okZLhB/Kr6FQTThFced0zSTacSPU1+SMfQ/DEc54thXOxwU1tkow== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1771256267; 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=6PnG3DeeB6mHo0hnnLDiezB/8Zfvc61iiF9yoYDdbs0=; b=sv9xFOQPVrfsm4wO3sVRTKH4Fig0un2FzAXsPkdWRfDOjsnrA/XNt3eTUFGBZOg/vCAZbh DYrPJautLl9o7SDg== From: Sebastian Andrzej Siewior To: Bert Karwatzki Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: "Dead loop on virtual device" error without softirq-BKL on PREEMPT_RT Message-ID: <20260216153745.CA3__zRc@linutronix.de> References: <20260216134333.412332-1-spasswolf@web.de> <6274de932f4a62c51b424b65fc875ef3cb5ffd60.camel@web.de> Precedence: bulk X-Mailing-List: linux-kernel@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: <6274de932f4a62c51b424b65fc875ef3cb5ffd60.camel@web.de> On 2026-02-16 16:32:29 [+0100], Bert Karwatzki wrote: > Am Montag, dem 16.02.2026 um 14:43 +0100 schrieb Bert Karwatzki: > > Starting with linux-6.18, I see the following log messages > > > > 2026-02-15T23:50:17.558716+01:00 [ T1559] Dead loop on virtual device wlp4s0, fix it urgently! > > 2026-02-15T23:50:17.558737+01:00 [ T1559] Dead loop on virtual device wlp4s0, fix it urgently! > > [...] > > > > regarding my wireless network device > > > > 04:00.0 Network controller [0280]: MEDIATEK Corp. MT7921K (RZ608) Wi-Fi 6E 80MHz [14c3:0608] > > > > I bisected this (from v6.17 to v6.18) and got this as the first bad commit: > > 3253cb49cbad ("softirq: Allow to drop the softirq-BKL lock on PREEMPT_RT") > > > > Using CONFIG_PREEMPT_RT_NEEDS_BH_LOCK=y in v6.18.10 fixes the issue. > > > > Bert Karwatzki > > May I presume that to fix this properly at least some of the spin_lock_bh()s in > net/mac80211/ need to be converted to local_lock_nested_bh()s? I am not sure what issue is so I can't tell. The dev_xmit_recursion*() based counters are per-task so it should be fine. But yet the wifi managed to repeatedly enqueue packets. This might be a real recursion, a stack trace should tell. And then, somewhere synchronisation is missing. > Bert Karwatzki Sebastian