Commit f6602a97 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'rcu-urgent.2022.10.20a' of... 

Merge tag 'rcu-urgent.2022.10.20a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU fix from Paul McKenney:
 "Fix a regression caused by commit bf95b2bc ("rcu: Switch polled
  grace-period APIs to ->gp_seq_polled"), which could incorrectly leave
  interrupts enabled after an early-boot call to synchronize_rcu().

  Such synchronize_rcu() calls must acquire leaf rcu_node locks in order
  to properly interact with polled grace periods, but the code did not
  take into account the possibility of synchronize_rcu() being invoked
  from the portion of the boot sequence during which interrupts are
  disabled.

  This commit therefore switches the lock acquisition and release from
  irq to irqsave/irqrestore"

* tag 'rcu-urgent.2022.10.20a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu: Keep synchronize_rcu() from enabling irqs in early boot
parents 2a91e897 31d8aaa8

kernel/rcu/tree.c

+6 −4
Original line number Diff line number Diff line
@@ -1403,30 +1403,32 @@ static void rcu_poll_gp_seq_end(unsigned long *snap) 
// where caller does not hold the root rcu_node structure's lock.

static void rcu_poll_gp_seq_start_unlocked(unsigned long *snap)

{

	unsigned long flags;

	struct rcu_node *rnp = rcu_get_root();



	if (rcu_init_invoked()) {

		lockdep_assert_irqs_enabled();

		raw_spin_lock_irq_rcu_node(rnp);

		raw_spin_lock_irqsave_rcu_node(rnp, flags);

	}

	rcu_poll_gp_seq_start(snap);

	if (rcu_init_invoked())

		raw_spin_unlock_irq_rcu_node(rnp);

		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

}



// Make the polled API aware of the end of a grace period, but where

// caller does not hold the root rcu_node structure's lock.

static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap)

{

	unsigned long flags;

	struct rcu_node *rnp = rcu_get_root();



	if (rcu_init_invoked()) {

		lockdep_assert_irqs_enabled();

		raw_spin_lock_irq_rcu_node(rnp);

		raw_spin_lock_irqsave_rcu_node(rnp, flags);

	}

	rcu_poll_gp_seq_end(snap);

	if (rcu_init_invoked())

		raw_spin_unlock_irq_rcu_node(rnp);

		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

}



/*