diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2025-09-08 18:00:05 -0700 |
|---|---|---|
| committer | Vlastimil Babka <vbabka@suse.cz> | 2025-09-29 09:42:36 +0200 |
| commit | 83382af9ddc3cb0ef43f67d049b461720ad785e6 (patch) | |
| tree | 590478f30d718084f7bead7e896ca56ea9b23be1 | |
| parent | d7242af8643409aae32243450341ef25b28d8a8c (diff) | |
slab: Make slub local_(try)lock more precise for LOCKDEP
kmalloc_nolock() can be called from any context
the ___slab_alloc() can acquire local_trylock_t (which is rt_spin_lock
in PREEMPT_RT) and attempt to acquire a different local_trylock_t
while in the same task context.
The calling sequence might look like:
kmalloc() -> tracepoint -> bpf -> kmalloc_nolock()
or more precisely:
__lock_acquire+0x12ad/0x2590
lock_acquire+0x133/0x2d0
rt_spin_lock+0x6f/0x250
___slab_alloc+0xb7/0xec0
kmalloc_nolock_noprof+0x15a/0x430
my_debug_callback+0x20e/0x390 [testmod]
___slab_alloc+0x256/0xec0
__kmalloc_cache_noprof+0xd6/0x3b0
Make LOCKDEP understand that local_trylock_t-s protect
different kmem_caches. In order to do that add lock_class_key
for each kmem_cache and use that key in local_trylock_t.
This stack trace is possible on both PREEMPT_RT and !PREEMPT_RT,
but teach lockdep about it only for PREEMPT_RT, since
in !PREEMPT_RT the ___slab_alloc() code is using
local_trylock_irqsave() when lockdep is on.
Note, this patch applies this logic to local_lock_t
while the next one converts it to local_trylock_t.
Both are mapped to rt_spin_lock in PREEMPT_RT.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
| -rw-r--r-- | mm/slab.h | 1 | ||||
| -rw-r--r-- | mm/slub.c | 20 |
2 files changed, 21 insertions, 0 deletions
diff --git a/mm/slab.h b/mm/slab.h index e82e51c44bd0..43245d9207b6 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -234,6 +234,7 @@ struct kmem_cache_order_objects { struct kmem_cache { #ifndef CONFIG_SLUB_TINY struct kmem_cache_cpu __percpu *cpu_slab; + struct lock_class_key lock_key; #endif struct slub_percpu_sheaves __percpu *cpu_sheaves; /* Used for retrieving partial slabs, etc. */ diff --git a/mm/slub.c b/mm/slub.c index 114ec18d223b..ee575ed9250f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3586,12 +3586,29 @@ static inline void note_cmpxchg_failure(const char *n, static void init_kmem_cache_cpus(struct kmem_cache *s) { +#ifdef CONFIG_PREEMPT_RT + /* + * Register lockdep key for non-boot kmem caches to avoid + * WARN_ON_ONCE(static_obj(key))) in lockdep_register_key() + */ + bool finegrain_lockdep = !init_section_contains(s, 1); +#else + /* + * Don't bother with different lockdep classes for each + * kmem_cache, since we only use local_trylock_irqsave(). + */ + bool finegrain_lockdep = false; +#endif int cpu; struct kmem_cache_cpu *c; + if (finegrain_lockdep) + lockdep_register_key(&s->lock_key); for_each_possible_cpu(cpu) { c = per_cpu_ptr(s->cpu_slab, cpu); local_lock_init(&c->lock); + if (finegrain_lockdep) + lockdep_set_class(&c->lock, &s->lock_key); c->tid = init_tid(cpu); } } @@ -7210,6 +7227,9 @@ void __kmem_cache_release(struct kmem_cache *s) if (s->cpu_sheaves) pcs_destroy(s); #ifndef CONFIG_SLUB_TINY +#ifdef CONFIG_PREEMPT_RT + lockdep_unregister_key(&s->lock_key); +#endif free_percpu(s->cpu_slab); #endif free_kmem_cache_nodes(s); |