[PATCH 1/2] slub: Enable backtrace for create/delete points.

greearb
2011-06-27T23:20:23Z

From: Ben Greear <greearb@candelatech.com>

This patch attempts to grab a backtrace for the creation
and deletion points of the slub object. When a fault is
detected, we can then get a better idea of where the item
was deleted.

Signed-off-by: Ben Greear <greearb@candelatech.com>
---
:100644 100644 35f351f... 14d0135... M mm/slub.c
mm/slub.c | 39 ++++++++++++++++++++++++++++++++-------
1 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 35f351f..14d0135 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -191,8 +191,10 @@ static LIST_HEAD(slab_caches);
/*
* Tracking user of a slab.
*/
+#define TRACK_ADDRS_COUNT 16
struct track {
- unsigned long addr; /* Called from address */
+ unsigned long caddr;
+ unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */
int cpu; /* Was running on cpu */
int pid; /* Pid context */
unsigned long when; /* When did the operation occur */
@@ -420,7 +422,24 @@ static void set_track(struct kmem_cache *s, void *object,
struct track *p = get_track(s, object, alloc);

if (addr) {
- p->addr = addr;
+ struct stack_trace trace;
+ int i;
+
+ trace.nr_entries = 0;
+ trace.max_entries = TRACK_ADDRS_COUNT;
+ trace.entries = p->addrs;
+ trace.skip = 3;
+ save_stack_trace(&trace);
+
+ /* See rant in lockdep.c */
+ if (trace.nr_entries != 0 &&
+ trace.entries[trace.nr_entries - 1] == ULONG_MAX)
+ trace.nr_entries--;
+
+ for (i = trace.nr_entries; i<TRACK_ADDRS_COUNT; i++)
+ p->addrs[i] = 0;
+
+ p->caddr = addr;
p->cpu = smp_processor_id();
p->pid = current->pid;
p->when = jiffies;
@@ -439,11 +458,17 @@ static void init_tracking(struct kmem_cache *s, void *object)

static void print_track(const char *s, struct track *t)
{
- if (!t->addr)
+ int i;
+ if (!t->caddr)
return;

printk(KERN_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->caddr, jiffies - t->when, t->cpu, t->pid);
+ for (i = 0; i < TRACK_ADDRS_COUNT; i++)
+ if (t->addrs[i])
+ printk(KERN_ERR "\t%pS\n", (void *)t->addrs[i]);
+ else
+ break;
}

static void print_tracking(struct kmem_cache *s, void *object)
@@ -3721,7 +3746,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
break;

caddr = t->loc[pos].addr;
- if (track->addr == caddr) {
+ if (track->caddr == caddr) {

l = &t->loc[pos];
l->count++;
@@ -3744,7 +3769,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
return 1;
}

- if (track->addr < caddr)
+ if (track->caddr < caddr)
end = pos;
else
start = pos;
@@ -3762,7 +3787,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
(t->count - pos) * sizeof(struct location));
t->count++;
l->count = 1;
- l->addr = track->addr;
+ l->addr = track->caddr;
l->sum_time = age;
l->min_time = age;
l->max_time = age;
--
1.7.3.4