diff --git a/mm/slub.c b/mm/slub.c index 28af56acc3ab..49223795a7d6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6265,11 +6265,29 @@ empty: free_empty_sheaf(s, sheaf); } +/* + * kvfree_call_rcu() can be called while holding a raw_spinlock_t. Since + * __kfree_rcu_sheaf() may acquire a spinlock_t (sleeping lock on PREEMPT_RT), + * this would violate lock nesting rules. Therefore, kvfree_call_rcu() avoids + * this problem by bypassing the sheaves layer entirely on PREEMPT_RT. + * + * However, lockdep still complains that it is invalid to acquire spinlock_t + * while holding raw_spinlock_t, even on !PREEMPT_RT where spinlock_t is a + * spinning lock. Tell lockdep that acquiring spinlock_t is valid here + * by temporarily raising the wait-type to LD_WAIT_CONFIG. + */ +static DEFINE_WAIT_OVERRIDE_MAP(kfree_rcu_sheaf_map, LD_WAIT_CONFIG); + bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj) { struct slub_percpu_sheaves *pcs; struct slab_sheaf *rcu_sheaf; + if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT))) + return false; + + lock_map_acquire_try(&kfree_rcu_sheaf_map); + if (!local_trylock(&s->cpu_sheaves->lock)) goto fail; @@ -6346,10 +6364,12 @@ do_free: local_unlock(&s->cpu_sheaves->lock); stat(s, FREE_RCU_SHEAF); + lock_map_release(&kfree_rcu_sheaf_map); return true; fail: stat(s, FREE_RCU_SHEAF_FAIL); + lock_map_release(&kfree_rcu_sheaf_map); return false; }