From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DF67C0650F for ; Thu, 8 Aug 2019 19:53:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 706942184E for ; Thu, 8 Aug 2019 19:53:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565294032; bh=0javQJG2N3SRtmKFfgxuYv2z4xXZJpn03rwbSlHoIYI=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=thQ3dc1zrjs2pvvebF03Qz2BZjDX6FJvr8qOa3XLfy/2Q7h/Tqp7fvvaqPSCBwfGJ xmx7hIity6TrUR3SqA/owXRPxJABuFxXhVv6SwHX4FcXhM6AhpeXfHTe6RmMfv6lqu vri9oADvlc4Y3MqalVeTUtgRn+FTjH+bb3X1YRog= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390244AbfHHTxv (ORCPT ); Thu, 8 Aug 2019 15:53:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:58228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404578AbfHHTx2 (ORCPT ); Thu, 8 Aug 2019 15:53:28 -0400 Received: from localhost.localdomain (c-98-220-238-81.hsd1.il.comcast.net [98.220.238.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6886C218F0; Thu, 8 Aug 2019 19:53:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565294007; bh=0javQJG2N3SRtmKFfgxuYv2z4xXZJpn03rwbSlHoIYI=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=AETXDqgdWcwPV8/00USmsuErKGQPUdHnHjBPGE4JmYeGqPXXyLZnKa4buFff9cpNA eElUd6YYElCI90r+2EdKJmMmUvju+X0mGuHp8sTVs3q5vvxGG8NTs9g24yfbEhZz1u wp7usgwid3Md1e8x/bwouZPJlTRl5HtK7Y0l4mBw= From: zanussi@kernel.org To: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Sebastian Andrzej Siewior , Daniel Wagner , Tom Zanussi , Julia Cartwright Subject: [PATCH RT 18/19] mm/zswap: Do not disable preemption in zswap_frontswap_store() Date: Thu, 8 Aug 2019 14:52:46 -0500 Message-Id: <15236d55deeb510c997d4057a4585eb6a755be80.1565293935.git.zanussi@kernel.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Luis Claudio R. Goncalves" v4.14.137-rt65-rc1 stable review patch. If anyone has any objections, please let me know. ----------- [ Upstream commit 4e4cf4be79635e67144632d9135286381acbc95a ] Zswap causes "BUG: scheduling while atomic" by blocking on a rt_spin_lock() with preemption disabled. The preemption is disabled by get_cpu_var() in zswap_frontswap_store() to protect the access of the zswap_dstmem percpu variable. Use get_locked_var() to protect the percpu zswap_dstmem variable, making the code preemptive. As get_cpu_ptr() also disables preemption, replace it by this_cpu_ptr() and remove the counterpart put_cpu_ptr(). Steps to Reproduce: 1. # grubby --args "zswap.enabled=1" --update-kernel DEFAULT 2. # reboot 3. Calculate the amount o memory to be used by the test: ---> grep MemAvailable /proc/meminfo ---> Add 25% ~ 50% to that value 4. # stress --vm 1 --vm-bytes ${MemAvailable+25%} --timeout 240s Usually, in less than 5 minutes the backtrace listed below appears, followed by a kernel panic: | BUG: scheduling while atomic: kswapd1/181/0x00000002 | | Preemption disabled at: | [] zswap_frontswap_store+0x21a/0x6e1 | | Kernel panic - not syncing: scheduling while atomic | CPU: 14 PID: 181 Comm: kswapd1 Kdump: loaded Not tainted 5.0.14-rt9 #1 | Hardware name: AMD Pence/Pence, BIOS WPN2321X_Weekly_12_03_21 03/19/2012 | Call Trace: | panic+0x106/0x2a7 | __schedule_bug.cold+0x3f/0x51 | __schedule+0x5cb/0x6f0 | schedule+0x43/0xd0 | rt_spin_lock_slowlock_locked+0x114/0x2b0 | rt_spin_lock_slowlock+0x51/0x80 | zbud_alloc+0x1da/0x2d0 | zswap_frontswap_store+0x31a/0x6e1 | __frontswap_store+0xab/0x130 | swap_writepage+0x39/0x70 | pageout.isra.0+0xe3/0x320 | shrink_page_list+0xa8e/0xd10 | shrink_inactive_list+0x251/0x840 | shrink_node_memcg+0x213/0x770 | shrink_node+0xd9/0x450 | balance_pgdat+0x2d5/0x510 | kswapd+0x218/0x470 | kthread+0xfb/0x130 | ret_from_fork+0x27/0x50 Cc: stable-rt@vger.kernel.org Reported-by: Ping Fang Signed-off-by: Luis Claudio R. Goncalves Reviewed-by: Daniel Bristot de Oliveira Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Tom Zanussi Conflicts: mm/zswap.c --- mm/zswap.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index ebb0bc88c5f7..a2b4e14f851c 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -953,6 +954,8 @@ static int zswap_shrink(void) return ret; } +/* protect zswap_dstmem from concurrency */ +static DEFINE_LOCAL_IRQ_LOCK(zswap_dstmem_lock); /********************************* * frontswap hooks **********************************/ @@ -1016,12 +1019,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, } /* compress */ - dst = get_cpu_var(zswap_dstmem); - tfm = *get_cpu_ptr(entry->pool->tfm); + dst = get_locked_var(zswap_dstmem_lock, zswap_dstmem); + tfm = *this_cpu_ptr(entry->pool->tfm); src = kmap_atomic(page); ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen); kunmap_atomic(src); - put_cpu_ptr(entry->pool->tfm); if (ret) { ret = -EINVAL; goto put_dstmem; @@ -1045,7 +1047,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, buf = (u8 *)(zhdr + 1); memcpy(buf, dst, dlen); zpool_unmap_handle(entry->pool->zpool, handle); - put_cpu_var(zswap_dstmem); + put_locked_var(zswap_dstmem_lock, zswap_dstmem); /* populate entry */ entry->offset = offset; @@ -1072,7 +1074,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, return 0; put_dstmem: - put_cpu_var(zswap_dstmem); + put_locked_var(zswap_dstmem_lock, zswap_dstmem); zswap_pool_put(entry->pool); freepage: zswap_entry_cache_free(entry); -- 2.14.1