From mboxrd@z Thu Jan 1 00:00:00 1970 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 60D8F17B50C; Fri, 29 Mar 2024 12:41:14 +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=1711716074; cv=none; b=sccdh99OMC55j8RtDJqkBpErNwwnfcNNko43VWNVqXP8v8mvxiPDN49QdmXxgedu+tkzlm8jrSHgd+RwQ9vfpDnQzoqu7LyujIZ6zLSwxKf42iH/YV7fuT6DWZatfbI/2s1gue/ZLKC7OaTY3CwTtU0vvINqJ8gzVzbGoEAuv/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711716074; c=relaxed/simple; bh=M5KWR1kOnUHwDGq3v++7oLxZFhzioC3ac36tmPcpu1M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DTljm5IgYR1EiHXNOKX3IHo8wnKJ8a1knfBSclus7UW3rFOsM2CtYeLxuwR71HFiZKuFI4c6r9nJ1D5Qgr2GbIYoX0Kn2dUTRK1vjGTZDqofsWNPlUZJdWMX571QFVMN1SmiXpyefRPZxpeANz9mgID8qahcIedLoQHlQFKGovQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=r3+fm6XY; 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="r3+fm6XY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1727BC43394; Fri, 29 Mar 2024 12:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711716074; bh=M5KWR1kOnUHwDGq3v++7oLxZFhzioC3ac36tmPcpu1M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r3+fm6XYf2ML0iUAlJWRDGcdrspBN7Zmeaw20VuTfdSosOsjSmihCyCkMwkPR6rgm wl4L2AuBblasqnC+DPX/cOpe/NS1YL4vo8BxjKdG1fd6OW3ppNHcmHUW1nfacFoUUw xorcaocq23N7oV4BX3JE8qGnjYRsjXE3K+ttg1ujfJc+Jmum5l0fzK0PFMfBysGD0f 7hFFPFFyI9gAQ/GA9y2V/CKzBdnHjIa/xD+TtS4tE/NffiuyX3zXYP5hH941N3F/qD Doe7/Kolq/S8eY2bq9cr/x+0DV3/h6JySpSNJQ4ThxqWg3EztmvLiXWmMagLBJ5K0z jBdoDL521vKTQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Zqiang , Joel Fernandes , Frederic Weisbecker , "Paul E . McKenney" , Boqun Feng , Sasha Levin , quic_neeraju@quicinc.com, josh@joshtriplett.org, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 6.8 40/98] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() Date: Fri, 29 Mar 2024 08:37:11 -0400 Message-ID: <20240329123919.3087149-40-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329123919.3087149-1-sashal@kernel.org> References: <20240329123919.3087149-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.8.2 Content-Transfer-Encoding: 8bit From: Zqiang [ Upstream commit dda98810b552fc6bf650f4270edeebdc2f28bd3f ] For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and CONFIG_RCU_LAZY=y, the following scenarios will trigger WARN_ON_ONCE() in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions: CPU2 CPU11 kthread rcu_nocb_cb_kthread ksys_write rcu_do_batch vfs_write rcu_torture_timer_cb proc_sys_write __kmem_cache_free proc_sys_call_handler kmemleak_free drop_caches_sysctl_handler delete_object_full drop_slab __delete_object shrink_slab put_object lazy_rcu_shrink_scan call_rcu rcu_nocb_flush_bypass __call_rcu_commn rcu_nocb_bypass_lock raw_spin_trylock(&rdp->nocb_bypass_lock) fail atomic_inc(&rdp->nocb_lock_contended); rcu_nocb_wait_contended WARN_ON_ONCE(smp_processor_id() != rdp->cpu); WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) | |_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ _ _ _ _ _ _ _ _ __| Reproduce this bug with "echo 3 > /proc/sys/vm/drop_caches". This commit therefore uses rcu_nocb_try_flush_bypass() instead of rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(). If the nocb_bypass queue is being flushed, then rcu_nocb_try_flush_bypass will return directly. Signed-off-by: Zqiang Reviewed-by: Joel Fernandes (Google) Reviewed-by: Frederic Weisbecker Reviewed-by: Paul E. McKenney Signed-off-by: Boqun Feng Signed-off-by: Sasha Levin --- kernel/rcu/tree_nocb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 4efbf7333d4e1..d430b4656f59e 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1383,7 +1383,7 @@ lazy_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) rcu_nocb_unlock_irqrestore(rdp, flags); continue; } - WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies, false)); + rcu_nocb_try_flush_bypass(rdp, jiffies); rcu_nocb_unlock_irqrestore(rdp, flags); wake_nocb_gp(rdp, false); sc->nr_to_scan -= _count; -- 2.43.0