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 609CF137934; Fri, 29 Mar 2024 12:44:23 +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=1711716263; cv=none; b=hPn0mJIyulzoLsjx4TzL8B34Ijxa26W0RN2iAY+iP7sPjaGWp2o4pFGhFoXabqd8FpJMiqePKvROj5Yi/5q/rU9OdsFcvFqxM+rqmmbJs6hbd9zu5y4sWvEUYgF6bBXJMeJ4lfjZs7b9/2Gihv90M+K0fkKeNt6AvbkfA7QJros= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711716263; c=relaxed/simple; bh=VCCXhfkVpDlHi/MWHIArZQ+F57QUhCgl7o4dhhoMGhQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EGbvRLhdkavWy5m+1eEysOi7Vkp1Fmw5MEjCzwFwZsudlAih5gsby02Itd7oWcB1zUGV3DLpD1geHmkRXL5GCUb95Yhq1CHq9H2HY3v3ZFyrQy5iMoK5qnMbhwv9ICyxdKIxs1RyKCoVI+4ahJsteS2N95stxx/xJMBaJ4UppaU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UXR7gqUr; 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="UXR7gqUr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19D24C433F1; Fri, 29 Mar 2024 12:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711716263; bh=VCCXhfkVpDlHi/MWHIArZQ+F57QUhCgl7o4dhhoMGhQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UXR7gqUr2HocNRY72BWuQv71xDXJWgwyJkaboGdLThfA0mNuOl94JpGqgs3Q4/+aN 2f73dkVOuzG4WWtaFlv9pccX73tRwWjF5qXuO8YuePIE88sHCji2ulvp36kS2LmKyg KO5ZHqHbxdg3TIGpXWhUZdZVO813/vRYSdBuQe48VsoeUhvXOXxXA3ur1XsdV1atV8 aS8OHa7ELIdpG/h2o8s12H2LUwT0ics//jk2nexicGhKxd5F8+r3JGW2WmnbgjYaU/ sF7JwuM/PN5J1ZzBeerce4i8USf47Dpcd//t+myC4zS6hgmFRB+Edmd4VGdYRR3xg+ y0qKYbrVYpAEg== 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 6.6 28/75] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() Date: Fri, 29 Mar 2024 08:42:09 -0400 Message-ID: <20240329124330.3089520-28-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329124330.3089520-1-sashal@kernel.org> References: <20240329124330.3089520-1-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 6.6.23 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 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