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@suse.cz: 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@linutronix.de>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/Yp9sqoUi4fVa5ExF@linutronix.de

diff --git a/mm/slub.c b/mm/slub.c
index e553502..a5b14c1 100644 (file)
--- 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 @@ next_object:
        }
 
        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);