On 6/7/22 17:20, Sebastian Andrzej Siewior wrote:
> The set_track() invocation in free_debug_processing() is invoked with
> acquired slab_lock(). The lock disables interrupts on PREEMPT_RT and
> this forbids to allocate memory which is done in stack_depot_save().
>
> Split set_track() into two parts: set_track_prepare() which allocate
> memory and set_track_update() which only performs the assignment of the
> trace data structure. Use set_track_prepare() before disabling
> interrupts.
>
> Fixes: 5cf909c553e9e ("mm/slub: use stackdepot to save stack trace in objects")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Thanks!
What about calling set_track_update() from set_track() so the assignments
are not duplicated, like this?
----8<----
>From c3fbd9cb11043c69f1073f438edd40d267f46cef Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Date: Tue, 7 Jun 2022 17:20:10 +0200
Subject: [PATCH] mm/slub: Move the stackdepot related allocation out of
IRQ-off section.
The set_track() invocation in free_debug_processing() is invoked with
acquired slab_lock(). The lock disables interrupts on PREEMPT_RT and
this forbids to allocate memory which is done in stack_depot_save().
Split set_track() into two parts: set_track_prepare() which allocate
memory and set_track_update() which only performs the assignment of the
trace data structure. Use set_track_prepare() before disabling
interrupts.
[ vbabka@xxxxxxx: make set_track() call set_track_update() instead of
open-coded assignments ]
Fixes: 5cf909c553e9e ("mm/slub: use stackdepot to save stack trace in objects")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Link: https://lore.kernel.org/r/Yp9sqoUi4fVa5ExF@xxxxxxxxxxxxx
---
mm/slub.c | 41 ++++++++++++++++++++++++++++++++++-------
1 file changed, 34 insertions(+), 7 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index e5535020e0fd..f3b1e19b81f2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -726,25 +726,48 @@ static struct track *get_track(struct kmem_cache *s, void *object,
return kasan_reset_tag(p + alloc);
}
-static void noinline set_track(struct kmem_cache *s, void *object,
- enum track_item alloc, unsigned long addr)
-{
- struct track *p = get_track(s, object, alloc);
-
#ifdef CONFIG_STACKDEPOT
+static noinline depot_stack_handle_t set_track_prepare(void)
+{
+ depot_stack_handle_t handle;
unsigned long entries[TRACK_ADDRS_COUNT];
unsigned int nr_entries;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
- p->handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
+ handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
+
+ return handle;
+}
+#else
+static inline depot_stack_handle_t set_track_prepare(void)
+{
+ return 0;
+}
#endif
+static void set_track_update(struct kmem_cache *s, void *object,
+ enum track_item alloc, unsigned long addr,
+ depot_stack_handle_t handle)
+{
+ struct track *p = get_track(s, object, alloc);
+
+#ifdef CONFIG_STACKDEPOT
+ p->handle = handle;
+#endif
p->addr = addr;
p->cpu = smp_processor_id();
p->pid = current->pid;
p->when = jiffies;
}
+static __always_inline void set_track(struct kmem_cache *s, void *object,
+ enum track_item alloc, unsigned long addr)
+{
+ depot_stack_handle_t handle = set_track_prepare();
+
+ set_track_update(s, object, alloc, addr, handle);
+}
+
static void init_tracking(struct kmem_cache *s, void *object)
{
struct track *p;
@@ -1373,6 +1396,10 @@ static noinline int free_debug_processing(
int cnt = 0;
unsigned long flags, flags2;
int ret = 0;
+ depot_stack_handle_t handle = 0;
+
+ if (s->flags & SLAB_STORE_USER)
+ handle = set_track_prepare();
spin_lock_irqsave(&n->list_lock, flags);
slab_lock(slab, &flags2);
@@ -1391,7 +1418,7 @@ static noinline int free_debug_processing(
}
if (s->flags & SLAB_STORE_USER)
- set_track(s, object, TRACK_FREE, addr);
+ set_track_update(s, object, TRACK_FREE, addr, handle);
trace(s, slab, object, 0);
/* Freepointer not overwritten by init_object(), SLAB_POISON moved it */
init_object(s, object, SLUB_RED_INACTIVE);
--
2.36.1
