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Urgent RCU pull request for v6.1

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This pull request contains a commit that fixes bf95b2bc3e ("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.
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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 bf95b2bc3e ("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
This commit is contained in:
Linus Torvalds 2022-10-24 12:33:30 -07:00
commit f6602a97a1
1 changed files with 6 additions and 4 deletions
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10
kernel/rcu/tree.c
View File

@ -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);
}
/*