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rcu: Diagnose extended sync_rcu_do_polled_gp() loops

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This commit dumps out state when the sync_rcu_do_polled_gp() function
loops more than expected.  This is a debugging aid.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-05-09 09:49:05 -07:00
parent ef4f9d9b92
commit 82e445697d
1 changed files with 6 additions and 1 deletions
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7
kernel/rcu/tree_exp.h
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@ -970,6 +970,7 @@ EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
static void sync_rcu_do_polled_gp(struct work_struct *wp)
{
unsigned long flags;
int i = 0;
struct rcu_node *rnp = container_of(wp, struct rcu_node, exp_poll_wq);
unsigned long s;
@ -979,8 +980,12 @@ static void sync_rcu_do_polled_gp(struct work_struct *wp)
raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
if (s == RCU_GET_STATE_COMPLETED)
return;
while (!poll_state_synchronize_rcu(s))
while (!poll_state_synchronize_rcu(s)) {
synchronize_rcu_expedited();
if (i == 10 || i == 20)
pr_info("%s: i = %d s = %lx gp_seq_polled = %lx\n", __func__, i, s, READ_ONCE(rcu_state.gp_seq_polled));
i++;
}
raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
s = rnp->exp_seq_poll_rq;
if (poll_state_synchronize_rcu(s))