Commit 54aacfe3 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Fix rcu_pending for PREEMPT_RT 



PREEMPT_RT redefines how standard spinlocks work, so local_irq_save() +
spin_lock() is no longer equivalent to spin_lock_irqsave(). Fortunately,
we don't strictly need to do it that way.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 082c7441

fs/bcachefs/rcu_pending.c

+11 −11
Original line number Diff line number Diff line
@@ -182,11 +182,6 @@ static inline void kfree_bulk(size_t nr, void ** p) 
	while (nr--)

		kfree(*p);

}



#define local_irq_save(flags)		\

do {					\

	flags = 0;			\

} while (0)

#endif



static noinline void __process_finished_items(struct rcu_pending *pending,
@@ -429,9 +424,15 @@ __rcu_pending_enqueue(struct rcu_pending *pending, struct rcu_head *head, 


	BUG_ON((ptr != NULL) != (pending->process == RCU_PENDING_KVFREE_FN));



	local_irq_save(flags);

	p = this_cpu_ptr(pending->p);

	spin_lock(&p->lock);

	/* We could technically be scheduled before taking the lock and end up

	 * using a different cpu's rcu_pending_pcpu: that's ok, it needs a lock

	 * anyways

	 *

	 * And we have to do it this way to avoid breaking PREEMPT_RT, which

	 * redefines how spinlocks work:

	 */

	p = raw_cpu_ptr(pending->p);

	spin_lock_irqsave(&p->lock, flags);

	rcu_gp_poll_state_t seq = __get_state_synchronize_rcu(pending->srcu);

restart:

	if (may_sleep &&
@@ -520,9 +521,8 @@ __rcu_pending_enqueue(struct rcu_pending *pending, struct rcu_head *head, 
		goto free_node;

	}



	local_irq_save(flags);

	p = this_cpu_ptr(pending->p);

	spin_lock(&p->lock);

	p = raw_cpu_ptr(pending->p);

	spin_lock_irqsave(&p->lock, flags);

	goto restart;

}