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 46F1D31A7F6 for ; Tue, 17 Feb 2026 09:57:04 +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=1771322225; cv=none; b=kyI5MqecJPj8S7bFiQW4D3PHXf0MhdLcnES4Knn1/h/YVR/hMmE+ckfxmoewgLdtNP17N35DG9YUR7QHu/8LsrrtqNNcXp+NUfiVA2K/uGg88irVnXwr7qP/LEPSUd9xc6dQqhYD1QMcuW+NoukTP0O3Vw0oePLrRTL7IPv7Chk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771322225; c=relaxed/simple; bh=hkerWcKdIcCqzfDLpw1AgO0apvcqwNOcWfx9p2C4e3g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Fojb1PCASuOeLZw0SUqME5+1ou+BdggMyDLxpM7j4wRV1Scr7K1hqW67EzhvcQpuCXDvpG+t+401OiZYqgctCpUjm4HCHl4fJAvDdcLWUOh0YI803xLljN7fcHi9bxzklFZ7C8FAZfs756QblL1DbLG1AB9EDnQMNnfoRfCnLAg= 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=wjA392KX; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=iqCD71ok; 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="wjA392KX"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="iqCD71ok" Date: Tue, 17 Feb 2026 10:57:00 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1771322222; 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=muhHTqVma6ZzeSs4ibzV6CiJ+E+n6aPPxXTE6apN0OI=; b=wjA392KX/CqQfg51m3a2a9NlyUP4zqQvSpNgBm+dFDc7JEm4PAM5I7df4CPM4dq03qWijY UJtvf3boNoorA0E/KLU2fpIO2Yjoa9SBKmQ9CJj9UyL3mpGxd86VVDwGYILm8in6nLG2oU YRI/xbaUOF6eu8gGiOPJxxifMuFGUL6FXxS5BpnBDMBxy9EPmIUTQo9gBZmjOk3+XoBxWP VLRQgzm2+LfFpqC58pZLIHOXGzarpxpXzpGkyGwWQX6GKwT+yYDo9DVjCDGTeb89QgXSKU a3soRH1dTfxyxcy3zpQPIu/FDbl6afByjePfvttdd7Nc0xt1P+BsVywzY7VrKw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1771322222; 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=muhHTqVma6ZzeSs4ibzV6CiJ+E+n6aPPxXTE6apN0OI=; b=iqCD71okUOYa3n6Yo8eFIz3XkiBMtvbUTDnqud4vNcsvLHTN8PiiAPImO51Ewdb3bB21eU 9oPCFra+tFlBLpDg== 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: <20260217095700.SjYjM8RO@linutronix.de> References: <20260216134333.412332-1-spasswolf@web.de> <6274de932f4a62c51b424b65fc875ef3cb5ffd60.camel@web.de> <20260216153745.CA3__zRc@linutronix.de> <37d6e27f96afb57c5716798530cb3560d25202e5.camel@web.de> <20260217071952.WCXLGs5-@linutronix.de> <80114792206dc00d0099f00999a209e717debb12.camel@web.de> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <80114792206dc00d0099f00999a209e717debb12.camel@web.de> On 2026-02-17 09:56:48 [+0100], Bert Karwatzki wrote: > Am Dienstag, dem 17.02.2026 um 08:19 +0100 schrieb Sebastian Andrzej Siewior: > > On 2026-02-17 00:48:25 [+0100], Bert Karwatzki wrote: > > > The problem seems to be that different preemtible threads try to send skbs. > > > > This does not matter because the counter is per-thread not per-CPU. > > The "Dead loop on virtual device" messages is not printed because dev_xmit_recursion() > returns true, but because READ_ONCE(txq->xmit_lock_owner) == cpu. Ach, so it is not the recursion, it is the assigned CPU. This is assigned via __netif_tx_lock(). Here we somehow lack the expected synchronisation. So the queue should be locked but not by the caller. > Here's the backtrace: thanks. > Bert Karwatzki Sebastian