From patchwork Tue Nov 21 12:33:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13462991 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20F56C61D92 for ; Tue, 21 Nov 2023 12:33:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231360AbjKUMd0 (ORCPT ); Tue, 21 Nov 2023 07:33:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229954AbjKUMd0 (ORCPT ); Tue, 21 Nov 2023 07:33:26 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9459C11C; Tue, 21 Nov 2023 04:33:19 -0800 (PST) Date: Tue, 21 Nov 2023 13:33:15 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1700569997; 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; bh=Fh9e3GaErBHGJCOCbK/EGCyKE1R80+6heNDm0N0TMWA=; b=wRATZsQk4Ria7Rl7ltcBbbJTT3Ilc9PeqBCPZJtujOZ9ckY4Js7fjsSeJU9HwCP6aSCSh2 Lz+cmtIpDw014hyQGiwFtek83644Yn9ATk2kff11HAdoTCSi9jjk9ZEnksd+0cew2jHMzO omoQiROzwzTLF9lpFXV1K6OGM8qB3U5BN4i2ndTscIr5ATXpb4ZK3cK0oFZs+eh/KESx+J Le/+rhkhh5EbMxWAVS45j7aAJ4vl/CDvxzLlBi6FpXdnNa7J9pojdjVjhrukpu0G21zKx3 AithaSGpHvriir/YVHTnrGR4PuURPQrb08QoYGGVTeUyMip7oO03TlImdsv34g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1700569997; 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; bh=Fh9e3GaErBHGJCOCbK/EGCyKE1R80+6heNDm0N0TMWA=; b=x+PC4P4BkaQPUae8UReQEYwUBsiT86OWBEWK14JS9Wj7In+IcXfjZsDaduUOuer4mu7mdd SuLm2Cxb4bdaQnCA== From: Sebastian Andrzej Siewior To: Peter Zijlstra Cc: Boqun Feng , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, "Paul E. McKenney" , Frederic Weisbecker , Ingo Molnar , Joel Fernandes , John Ogness , Josh Triplett , Lai Jiangshan , Mathieu Desnoyers , Neeraj Upadhyay , Steven Rostedt , Thomas Gleixner , Waiman Long , Will Deacon , Zqiang Subject: [REPOST PATCH] srcu: Use try-lock lockdep annotation for NMI-safe access. Message-ID: <20231121123315.egrgopGN@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org It is claimed that srcu_read_lock_nmisafe() NMI-safe. However it triggers a lockdep if used from NMI because lockdep expects a deadlock since nothing disables NMIs while the lock is acquired. Use a try-lock annotation for srcu_read_lock_nmisafe() to avoid lockdep complains if used from NMI. Fixes: f0f44752f5f61 ("rcu: Annotate SRCU's update-side lockdep dependencies") Link: https://lore.kernel.org/r/20230927160231.XRCDDSK4@linutronix.de Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Boqun Feng --- This is a repost of https://lore.kernel.org/r/20230927160231.XRCDDSK4@linutronix.de Based on the discussion there I *think* this is preferred over the NMI check in lock_acquire(). But then PeterZ also pointed out that he has a problem with f0f44752f5f61 ("rcu: Annotate SRCU's update-side lockdep dependencies") because trace_.*_rcuidle machinery. This looks okay because the _rcuidle part is using SRCU and the rcu_dereference_raw() tracepoint_func is using RCU + SRCU in its free part. include/linux/rcupdate.h | 6 ++++++ include/linux/srcu.h | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -301,6 +301,11 @@ static inline void rcu_lock_acquire(stru lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); } +static inline void rcu_try_lock_acquire(struct lockdep_map *map) +{ + lock_acquire(map, 0, 1, 2, 0, NULL, _THIS_IP_); +} + static inline void rcu_lock_release(struct lockdep_map *map) { lock_release(map, _THIS_IP_); @@ -315,6 +320,7 @@ int rcu_read_lock_any_held(void); #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ # define rcu_lock_acquire(a) do { } while (0) +# define rcu_try_lock_acquire(a) do { } while (0) # define rcu_lock_release(a) do { } while (0) static inline int rcu_read_lock_held(void) --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -229,7 +229,7 @@ static inline int srcu_read_lock_nmisafe srcu_check_nmi_safety(ssp, true); retval = __srcu_read_lock_nmisafe(ssp); - rcu_lock_acquire(&ssp->dep_map); + rcu_try_lock_acquire(&ssp->dep_map); return retval; }