From 86609d3319ad57ff65c20890391a035acad47bb1 Mon Sep 17 00:00:00 2001 From: Chintan Pandya Date: Thu, 5 Apr 2018 16:20:15 -0700 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: ============================================================================= BUG kmalloc-256 (Tainted: G W O ): Poison overwritten ----------------------------------------------------------------------------- ... INFO: Allocated in binder_transaction+0x4b0/0x2448 age=731 cpu=3 pid=5314 ... INFO: Freed in binder_free_transaction+0x2c/0x58 age=735 cpu=6 pid=2079 ... 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. New output will exactly be same. 'age' is still staying with single jiffies ref in both prints. Change-Id: I0846565807a4229748649bbecb1ffb743d71fcd8 Link: http://lkml.kernel.org/r/1520492010-19389-1-git-send-email-cpandya@codeaurora.org Signed-off-by: Chintan Pandya Acked-by: Christoph Lameter Reviewed-by: Andrew Morton Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slub.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'mm/slub.c') diff --git a/mm/slub.c b/mm/slub.c index e381728a3751..d92218ed7f1c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -598,13 +598,13 @@ static void init_tracking(struct kmem_cache *s, void *object) 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, struct track *t) 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) -- cgit v1.2.3-55-g7522