On 8/10/23 9:16 PM, Vlastimil Babka wrote:
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On 8/10/23 12:03, Vlastimil Babka wrote:
On 8/10/23 09:47, Xiaolei Wang wrote:
The kmemleak_late_init() is defined as a late_initcall. The current
implementation of set_track_prepare() depends on the kmemleak init.
That also means there is no call trace for the memory leak which object
is created before the kmemleak_late_init().
So if I understand correctly, we have the following sequence of events durin
boot
...
A: stack_depot is initialized
...
B: kmemleak is initialized
...
before this patchset, we can miss allocations before B, aftewards only
before A (which can't be helped), so we now have between A and B.
That's nice, but it's weird that can record kmemleak when
!kmemleak_initialized. Why can't it be initialized sooner in that case?
Looking closer, I think what you want could be achieved by kmemleak_init()
setting a variable that is checked in kmemleak_initialized() instead of the
kmemleak_initialized that's set too late.
I think this should work because:
- I assume kmemleak can't record anything before kmemleak_init()
- stack depot early init is requested one way or the other
- mm_core_init() calls stack_depot_early_init() before kmemleak_init()
But I also wonder how kmemleak can even reach set_track_prepare() before
kmemleak_init(), maybe that's the issue?
Before kmemleak_init, many places also need to allocate kmemleak_object,
and also need to save stack in advance, but kmemleak_object is allocated
in the form of an array, after kmemleak_init 'object_cache =
KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);'
I think there is still some memory not recorded on the backtrace before
stack_depot_early_init(), does anyone have a better suggestion?
thanks
xiaolei
In a previous patch, we have fixed a bug in stack_depot_save() so that
it can be invoked even before stack depot is initialized. So there is
no reason to check the kmemleak_initialized in set_track_prepare().
So delete the kmemleak_initialized judgment in set_track_prepare()
unreferenced object 0xc674ca80 (size 64):
comm "swapper/0", pid 1, jiffies 4294938337 (age 204.880s)
hex dump (first 32 bytes):
80 55 75 c6 80 54 75 c6 00 55 75 c6 80 52 75 c6 .Uu..Tu..Uu..Ru.
00 53 75 c6 00 00 00 00 00 00 00 00 00 00 00 00 .Su..........
Fixes: 56a61617dd22 ("mm: use stack_depot for recording kmemleak's backtrace")
Signed-off-by: Xiaolei Wang <xiaolei.wang@xxxxxxxxxxxxx>
---
mm/kmemleak.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index a2d34226e3c8..c9f2f816db19 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -610,8 +610,6 @@ static noinline depot_stack_handle_t set_track_prepare(void)
unsigned long entries[MAX_TRACE];
unsigned int nr_entries;
- if (!kmemleak_initialized)
- return 0;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
