The patch titled
Subject: mm/slub.c: use jitter-free reference while printing age
has been added to the -mm tree. Its filename is
slub-use-jitter-free-reference-while-printing-age.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slub-use-jitter-free-reference-while-printing-age.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slub-use-jitter-free-reference-while-printing-age.patch
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------------------------------------------------------
From: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
Subject: mm/slub.c: use jitter-free reference while printing age
When SLUB_DEBUG catches some issues, it prints all the required debug
info. However, in a few cases where allocation and free of the object has
happened in a very short time, 'age' might be misleading. See the example
below:
[ 6044.137581] =============================================================================
[ 6044.145863] BUG kmalloc-256 (Tainted: G W O ): Poison overwritten
[ 6044.152889] -----------------------------------------------------------------------------
...
[ 6044.170804] INFO: Allocated in binder_transaction+0x4b0/0x2448 age=731 cpu=3 pid=5314
...
[ 6044.216696] INFO: Freed in binder_free_transaction+0x2c/0x58 age=735 cpu=6 pid=2079
...
[ 6044.494293] Object fffffff14956a870: 6b 6b 6b 6b 6b 6b 6b 6b 67 6b 6b 6b 6b 6b 6b a5 kkkkkkkkgkkkk
In this case, object got freed later but 'age' shows otherwise. This
could be because, while printing this info, we print allocation traces
first and free traces thereafter. In between, if we get schedule out or
jiffies increment, (jiffies - t->when) could become meaningless.
Use the jitter free reference to calculate age.
Change-Id: I0846565807a4229748649bbecb1ffb743d71fcd8
Link: http://lkml.kernel.org/r/1520492010-19389-1-git-send-email-cpandya@xxxxxxxxxxxxxx
Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN mm/slub.c~slub-use-jitter-free-reference-while-printing-age mm/slub.c
--- a/mm/slub.c~slub-use-jitter-free-reference-while-printing-age
+++ a/mm/slub.c
@@ -598,13 +598,13 @@ static void init_tracking(struct kmem_ca
set_track(s, object, TRACK_ALLOC, 0UL);
}
-static void print_track(const char *s, struct track *t)
+static void print_track(const char *s, struct track *t, unsigned long pr_time)
{
if (!t->addr)
return;
pr_err("INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
- s, (void *)t->addr, jiffies - t->when, t->cpu, t->pid);
+ s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid);
#ifdef CONFIG_STACKTRACE
{
int i;
@@ -619,11 +619,12 @@ static void print_track(const char *s, s
static void print_tracking(struct kmem_cache *s, void *object)
{
+ unsigned long pr_time = jiffies;
if (!(s->flags & SLAB_STORE_USER))
return;
- print_track("Allocated", get_track(s, object, TRACK_ALLOC));
- print_track("Freed", get_track(s, object, TRACK_FREE));
+ print_track("Allocated", get_track(s, object, TRACK_ALLOC), pr_time);
+ print_track("Freed", get_track(s, object, TRACK_FREE), pr_time);
}
static void print_page_info(struct page *page)
_
Patches currently in -mm which might be from cpandya@xxxxxxxxxxxxxx are
slub-use-jitter-free-reference-while-printing-age.patch
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