From 54aacfe3976893ee04582a0bd61967bbee5a7e04 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Sun, 8 Jun 2025 12:17:02 -0400 Subject: [PATCH] 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: Kent Overstreet --- fs/bcachefs/rcu_pending.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/fs/bcachefs/rcu_pending.c b/fs/bcachefs/rcu_pending.c index bef2aa1b8bcd..b1438be9d690 100644 --- a/fs/bcachefs/rcu_pending.c +++ b/fs/bcachefs/rcu_pending.c @@ -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 @@ check_expired: 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; } -- 2.25.1