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 4876213FD94; Thu, 11 Apr 2024 10:27:26 +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=1712831246; cv=none; b=PdEoF05vT2mGy8HfvIBuF8YUhECBiEV2/UYIOofVp/lme/YpH+oQ1qpJCDeE+YS0LJuRdbYPrdLd0YFyrQnjWFVyIunXl6t/EnuxwsDzrK3mNo0bRVPKDx9qysRoCCOBEZPrmHo/CX2AV/6yyg+y1dy3J8zax3MUokk2jQNeSDo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712831246; c=relaxed/simple; bh=3ma+WmFDuhLz0Xuo5+rBx3eakHq/dgAHAACGl6tomh8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dZs8bPDoh0BtWZwOP499/fH+W/3qE+OkNETfyXvybZ7503ndy/uS+9CMpOTCuAXXeCaRxbb6uny7kPyMFe2cO/Ya2b2p1Dv69ddv0Hz2gukr8xcEEid9SZw/AqIxn8Po7dBhw0OOEsLo2JQT4Obr9bft8aPrTb75vDYpxp5zqvU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iC8T7dkB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="iC8T7dkB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 931A3C433C7; Thu, 11 Apr 2024 10:27:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712831246; bh=3ma+WmFDuhLz0Xuo5+rBx3eakHq/dgAHAACGl6tomh8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iC8T7dkBkizRvn4afhSR72RUl29JsvNcBIiE2IbWvd2+EYueor6nPuueuFq1zJ7zS VfrzaG2YQiwBk3K9rkX4dnswvEGJzAV1ly37uHdsM83Djm0xbBFw0wKr7JeVkYfwHz xSaudEtRWV5koI6vc2WInW9SwAAazhCfPrn50dVk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zqiang , "Joel Fernandes (Google)" , Frederic Weisbecker , "Paul E. McKenney" , Boqun Feng , Sasha Levin Subject: [PATCH 6.6 056/114] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() Date: Thu, 11 Apr 2024 11:56:23 +0200 Message-ID: <20240411095418.576956732@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240411095416.853744210@linuxfoundation.org> References: <20240411095416.853744210@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ 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 5598212d1f274..2b24405b9cd2b 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