On Tue, Jun 07, 2022 at 05:20:10PM +0200, 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().
Thanks, nice catch.
> 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>
> ---
> mm/slub.c | 39 +++++++++++++++++++++++++++++++++------
> 1 file changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index e5535020e0fdf..ee0445ccb288c 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -726,19 +726,42 @@ 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)
> +static noinline depot_stack_handle_t set_track_prepare(void)
> {
> - struct track *p = get_track(s, object, alloc);
> -
> + depot_stack_handle_t handle = 0;
> #ifdef CONFIG_STACKDEPOT
> 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);
> #endif
> + return handle;
> +}
>
> +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)
> +{
> + struct track *p = get_track(s, object, alloc);
> +
> +#ifdef CONFIG_STACKDEPOT
> + p->handle = set_track_prepare();
> +#endif
> p->addr = addr;
> p->cpu = smp_processor_id();
> p->pid = current->pid;
> @@ -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
>
Looks good to me.
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
--
Thanks,
Hyeonggon
