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 3F9003AEF2B for ; Thu, 19 Mar 2026 08:55:52 +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=1773910554; cv=none; b=KSKzY1hmEHZCRoLumNed47IRZRShuBRtzjfZyIk9kBwx/pkIyyFQ1a+P0WPVCjZ+6n6pl4WW/Wpfjw1b5bzhJFhsa19ZhE6ygDYj/a4o7z/LhZoN4Fsxta5Fw5JbZLDCAup1jOdyog2YyR+JjB2WMYsZGVHI+QNHN/VbLMil7v8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773910554; c=relaxed/simple; bh=vKZ+9LuApyI3XqByfvlkZsBHReacjiGEfFSRdwvj0eQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=u8oKXUIgxKikHz3mp48fxQGRDUcN9GVj91F99ocW55PvI3d2F7iYQv6tx+WsWxQeH1feTFiE4mZSso4lBnWktpMlw+fcZ578WIOS45j3MTTWMjw8okGOiQaTgHi7uokxwa6Y0QMPTe6LdcXNXpzqAF70+TRnSDyC+vrF2gsfOi4= 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=wtR4bD9E; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=SM3NZRra; 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="wtR4bD9E"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="SM3NZRra" Date: Thu, 19 Mar 2026 09:55:48 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1773910549; 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=7ZFb4WS4Gr4h5BF+zJIFWWqiuFSBdiKDJXSRz7oqNnw=; b=wtR4bD9Euzpr7RRv8SzjlVeJ5/9O0DMwhp9t+PAQ8lNsHad2FxU4kgo7JDgkJ7Bd9Z7PRu p0ZmMcnXzPN/BtDohBmiLPKbTT+pzTymJpqUGYdpFZ64RxBgDauNz81+49iW/WYIRx+qi6 vwc9Vk3BVRl1+oWew6gQbh3s69wp6cvS+mUqmUhMRZ+iVMQA5oAKbH16Bze28FDSfcRfRd OD+R8RbozecTauU3Ta0s39deSTxmCRgUATnCteHP4JBEtJlYsez1lRU5slgKYXzOf8yBLB Voi6NKb6qoBsxMf2U4c1sGgEcy0JLgVuaYXpB29xCFNiCewYy/vckJM3xbs+VQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1773910549; 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=7ZFb4WS4Gr4h5BF+zJIFWWqiuFSBdiKDJXSRz7oqNnw=; b=SM3NZRramZE0HMUh1UAakoj9YTqXTKuaIXY0plsUgsdBJeRKUqoIVztprvyhT5+rTqG9bm iBbuCGgZZZSk5xDw== From: Sebastian Andrzej Siewior To: "Paul E. McKenney" Cc: frederic@kernel.org, neeraj.iitr10@gmail.com, urezki@gmail.com, joelagnelf@nvidia.com, boqun.feng@gmail.com, rcu@vger.kernel.org, Kumar Kartikeya Dwivedi Subject: Re: Next-level bug in SRCU implementation of RCU Tasks Trace + PREEMPT_RT Message-ID: <20260319085548.UZQk1cyW@linutronix.de> References: <20260318105058.j2aKncBU@linutronix.de> <20260318144305.xI6RDtzk@linutronix.de> <76ef9a5e-7343-4b8e-bf3c-cabd8753ecdb@paulmck-laptop> <20260318160445.IyUiWV0T@linutronix.de> <06a0cb91-1737-4691-a810-8340e1acf1d6@paulmck-laptop> <20260318164710.gUolNYgg@linutronix.de> <9b685d13-5496-4bc9-ab6a-508bd4bf0f16@paulmck-laptop> Precedence: bulk X-Mailing-List: rcu@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: <9b685d13-5496-4bc9-ab6a-508bd4bf0f16@paulmck-laptop> On 2026-03-18 11:48:56 [-0700], Paul E. McKenney wrote: > We would need a lockless enqueue, which we have in llist.h. Only if CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG. Otherwise you must not provide call_rcu_nmi(). > The irq-work to actually do the call_rcu() or similar. reasonable. > There would also need to be rcu_barrier() changes, for example, to > drain all the llists. > > > I mean I am curious here who needs it any why ;) > > You got it right above, BPF. ;-) > > They currently check in_nmi() and to the irq-work step themselves. Then it would make sense since you do actually have users. > Thanx, Paul Sebastian