From: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: dave.hansen@intel.com,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] fork: Improve error message for corrupted page tables
Date: Tue, 30 Jul 2019 15:18:20 -0700 [thread overview]
Message-ID: <20190730221820.7738-1-sai.praneeth.prakhya@intel.com> (raw)
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). Hence, improve the
error message so that it's more informative.
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
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Suggested-by/Acked-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
---
include/linux/mm_types_task.h | 7 +++++++
kernel/fork.c | 4 ++--
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h
index d7016dcb245e..881f4ea3a1b5 100644
--- a/include/linux/mm_types_task.h
+++ b/include/linux/mm_types_task.h
@@ -44,6 +44,13 @@ enum {
NR_MM_COUNTERS
};
+static const char * const resident_page_types[NR_MM_COUNTERS] = {
+ "MM_FILEPAGES",
+ "MM_ANONPAGES",
+ "MM_SWAPENTS",
+ "MM_SHMEMPAGES",
+};
+
#if USE_SPLIT_PTE_PTLOCKS && defined(CONFIG_MMU)
#define SPLIT_RSS_COUNTING
/* per-thread cached information, */
diff --git a/kernel/fork.c b/kernel/fork.c
index 2852d0e76ea3..6aef5842d4e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -649,8 +649,8 @@ 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))
--
2.19.1
next reply other threads:[~2019-07-30 22:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 22:18 Sai Praneeth Prakhya [this message]
2019-07-31 22:27 ` [PATCH] fork: Improve error message for corrupted page tables Andrew Morton
2019-07-31 22:36 ` Sai Praneeth Prakhya
2019-08-01 4:20 ` Andrew Morton
2019-08-02 6:46 ` Prakhya, Sai Praneeth
2019-08-05 13:28 ` Vlastimil Babka
2019-08-06 3:09 ` Sai Praneeth Prakhya
2019-08-01 5:48 ` Anshuman Khandual
2019-08-02 6:52 ` Prakhya, Sai Praneeth
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