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authorSai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>2019-09-25 16:47:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-25 17:51:40 -0700
commit8495f7e6732ed248b648d36439795b42ec650b9e (patch)
tree6bf586c2f23b31c2f908ed3b19536099e066b4b0 /kernel/fork.c
parentaadc4e01dbaaccd38abde03bc84d0332a6bd9eab (diff)
fork: improve error message for corrupted page tables
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. Link: http://lkml.kernel.org/r/da75b5153f617f4c5739c08ee6ebeb3d19db0fbc.1565123758.git.sai.praneeth.prakhya@intel.com Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Suggested-by: Dave Hansen <dave.hansen@intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Dave Hansen <dave.hansen@intel.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 5a0fd518e04e..60763c043aa3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -125,6 +125,15 @@ int nr_threads; /* The idle threads do not count.. */
static int max_threads; /* tunable limit on nr_threads */
+#define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
+
+static const char * const resident_page_types[] = {
+ NAMED_ARRAY_INDEX(MM_FILEPAGES),
+ NAMED_ARRAY_INDEX(MM_ANONPAGES),
+ NAMED_ARRAY_INDEX(MM_SWAPENTS),
+ NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
+};
+
DEFINE_PER_CPU(unsigned long, process_counts) = 0;
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
@@ -645,12 +654,15 @@ static void check_mm(struct mm_struct *mm)
{
int i;
+ BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
+ "Please make sure 'struct resident_page_types[]' is updated as well");
+
for (i = 0; i < NR_MM_COUNTERS; i++) {
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))