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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 74453C433FF for ; Tue, 6 Aug 2019 03:08:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EE27214C6 for ; Tue, 6 Aug 2019 03:08:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731528AbfHFDIl (ORCPT ); Mon, 5 Aug 2019 23:08:41 -0400 Received: from mga02.intel.com ([134.134.136.20]:6367 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730036AbfHFDIl (ORCPT ); Mon, 5 Aug 2019 23:08:41 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Aug 2019 20:08:41 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,352,1559545200"; d="scan'208";a="168166998" Received: from sai-dev-mach.sc.intel.com ([143.183.140.153]) by orsmga008.jf.intel.com with ESMTP; 05 Aug 2019 20:08:40 -0700 From: Sai Praneeth Prakhya To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: dave.hansen@intel.com, Sai Praneeth Prakhya , Ingo Molnar , Vlastimil Babka , Peter Zijlstra , Andrew Morton , Anshuman Khandual Subject: [PATCH V2] fork: Improve error message for corrupted page tables Date: Mon, 5 Aug 2019 20:05:27 -0700 Message-Id: <3ef8a340deb1c87b725d44edb163073e2b6eca5a.1565059496.git.sai.praneeth.prakhya@intel.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a user process exits, the kernel cleans up the mm_struct of the user process and during cleanup, check_mm() checks the page tables of the user process for corruption (E.g: unexpected page flags set/cleared). For corrupted page tables, the error message printed by check_mm() isn't very clear as it prints the loop index instead of page table type (E.g: Resident file mapping pages vs Resident shared memory pages). The loop index in check_mm() is used to index rss_stat[] which represents individual memory type stats. Hence, instead of printing index, print memory type, thereby improving error message. Without patch: -------------- [ 204.836425] mm/pgtable-generic.c:29: bad p4d 0000000089eb4e92(800000025f941467) [ 204.836544] BUG: Bad rss-counter state mm:00000000f75895ea idx:0 val:2 [ 204.836615] BUG: Bad rss-counter state mm:00000000f75895ea idx:1 val:5 [ 204.836685] BUG: non-zero pgtables_bytes on freeing mm: 20480 With patch: ----------- [ 69.815453] mm/pgtable-generic.c:29: bad p4d 0000000084653642(800000025ca37467) [ 69.815872] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_FILEPAGES val:2 [ 69.815962] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_ANONPAGES val:5 [ 69.816050] BUG: non-zero pgtables_bytes on freeing mm: 20480 Also, change print function (from printk(KERN_ALERT, ..) to pr_alert()) so that it matches the other print statement. Cc: Ingo Molnar Cc: Vlastimil Babka Cc: Peter Zijlstra Cc: Andrew Morton Cc: Anshuman Khandual Acked-by: Dave Hansen Suggested-by: Dave Hansen Signed-off-by: Sai Praneeth Prakhya --- Changes from V1 to V2: ---------------------- 1. Move struct definition from header file to fork.c file, so that it won't be included in every compilation unit. As this struct is used *only* in fork.c, include the definition in fork.c itself. 2. Index the struct to match respective macros. 3. Mention about print function change in commit message. kernel/fork.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index d8ae0f1b4148..f34f441c50c0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -125,6 +125,13 @@ int nr_threads; /* The idle threads do not count.. */ static int max_threads; /* tunable limit on nr_threads */ +static const char * const resident_page_types[NR_MM_COUNTERS] = { + [MM_FILEPAGES] = "MM_FILEPAGES", + [MM_ANONPAGES] = "MM_ANONPAGES", + [MM_SWAPENTS] = "MM_SWAPENTS", + [MM_SHMEMPAGES] = "MM_SHMEMPAGES", +}; + DEFINE_PER_CPU(unsigned long, process_counts) = 0; __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ @@ -649,8 +656,8 @@ static void check_mm(struct mm_struct *mm) long x = atomic_long_read(&mm->rss_stat.count[i]); if (unlikely(x)) - printk(KERN_ALERT "BUG: Bad rss-counter state " - "mm:%p idx:%d val:%ld\n", mm, i, x); + pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", + mm, resident_page_types[i], x); } if (mm_pgtables_bytes(mm)) -- 2.7.4