From nobody Sun Feb 8 21:20:43 2026 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 28CED1E505; Fri, 30 Jan 2026 01:30:44 +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=1769736645; cv=none; b=YehBYzaX6uGsBJo/9dY4rmXSUHhnLYhZyuoX2Q1qlgt1Va7joFmkw4mV+ANUCOgau7EVmoOCw6EwnwMBb2xNLZV21EEsfo3cMklXoqFLuFjXTx+NlFvPzUGdMTSHdau9XtPdW5j9DjnfCms4e+bhtzZbMAxidbIak/BzqLK3VIc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769736645; c=relaxed/simple; bh=OlbIY1iyiqrtSFOkHZza6Io4EhPQz9j1A+bmxl8z/gw=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=gKB9bOmQRbW+gcyK/jU/hJPSXkMOFtgnDl6tGvlQYaq7rHDp8qvAJaqRQfNgP5O655j0f4hOGPAt0KcEDSuo0MY88/SUrwIvH+syBc4azxAMA3+gSAuSFkKzwZY++VFq6YUJlSTbx9uKwSk+JsIRBgxA3dhaQdYCSOS2XRaIxlg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HgCIg8pv; 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="HgCIg8pv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93CF7C4CEF7; Fri, 30 Jan 2026 01:30:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769736644; bh=OlbIY1iyiqrtSFOkHZza6Io4EhPQz9j1A+bmxl8z/gw=; h=Date:From:To:Cc:Subject:Reply-To:From; b=HgCIg8pv0gbrfouykuJ5fk91Ebam7hEIaXvEM3JrKnGuFXoHb8vDpXYESYqUZAFGM 3PTlcaWnMTkWFbEpEM/leXTYrgDq6S9nGGW2R10/CZdg8RBuzOAI6/exbtXVhQqrb+ TI6nnJYf27WUIQDbqQR3xpzaMt4I0nQI/Piz5BEoQoEIz25XdrHwQ4x3POdX2GhUdq +dGr57u+Q/odwT1O/31fg2PcIJ9RqIiMxUXiqsijzLWZ3o3sZdF5YKuXdTRFIr1eox lIHNdctrhWqAWTx6qTPlt4l50mCi65TH1wDJIEAUPtzs7qH3tBzlIQLfWHp/3xSyZF oFprhQWfvtyMQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 34AD9CE38F0; Thu, 29 Jan 2026 17:30:44 -0800 (PST) Date: Thu, 29 Jan 2026 17:30:44 -0800 From: "Paul E. McKenney" To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, bpf@vger.kernel.org, Andrii Nakryiko , Alexei Starovoitov , Peter Zijlstra , Boqun Feng Subject: [PATCH] srcu: Fix warning to permit SRCU-fast readers in NMI handlers Message-ID: <8232efe8-a7a3-446c-af0b-19f9b523b4f7@paulmck-laptop> Reply-To: paulmck@kernel.org Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" srcu: Fix warning to permit SRCU-fast readers in NMI handlers SRCU-fast is designed to be used in NMI handlers, even going so far as to use atomic operations for architectures supporting NMIs but not providing NMI-safe per-CPU atomic operations. However, the WARN_ON_ONCE() in __srcu_check_read_flavor() complains if SRCU-fast is used in an NMI handler. This commit therefore modifies that WARN_ON_ONCE() to avoid such complaints. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Tested-by: Steven Rostedt Cc: Andrii Nakryiko Cc: Alexei Starovoitov Cc: Peter Zijlstra Cc: bpf@vger.kernel.org diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index c469c708fdd6a..66ba6a2f83d3a 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -789,7 +789,8 @@ void __srcu_check_read_flavor(struct srcu_struct *ssp, = int read_flavor) struct srcu_data *sdp; =20 /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor value= s. */ - WARN_ON_ONCE((read_flavor !=3D SRCU_READ_FLAVOR_NMI) && in_nmi()); + WARN_ON_ONCE(read_flavor !=3D SRCU_READ_FLAVOR_NMI && + read_flavor !=3D SRCU_READ_FLAVOR_FAST && in_nmi()); WARN_ON_ONCE(read_flavor & (read_flavor - 1)); =20 sdp =3D raw_cpu_ptr(ssp->sda);