From: "Paul E. McKenney" <paulmck@kernel.org> stable inclusion from stable-v5.10.95 commit 12d3389b7af68d89e45b214640699fb603e243e3 bugzilla: https://gitee.com/openeuler/kernel/issues/I55EDV Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 614ddad17f22a22e035e2ea37a04815f50362017 upstream. Currently, rcu_advance_cbs_nowake() checks that a grace period is in progress, however, that grace period could end just after the check. This commit rechecks that a grace period is still in progress while holding the rcu_node structure's lock. The grace period cannot end while the current CPU's rcu_node structure's ->lock is held, thus avoiding false positives from the WARN_ON_ONCE(). As Daniel Vacek noted, it is not necessary for the rcu_node structure to have a CPU that has not yet passed through its quiescent state. Tested-by: Guillaume Morin <guillaume@morinfr.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yu Liao <liaoyu15@huawei.com> Reviewed-by: Wei Li <liwei391@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- kernel/rcu/tree.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b9c45b2d7690..1116ebf5715b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1601,10 +1601,11 @@ static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp, struct rcu_data *rdp) { rcu_lockdep_assert_cblist_protected(rdp); - if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || - !raw_spin_trylock_rcu_node(rnp)) + if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || !raw_spin_trylock_rcu_node(rnp)) return; - WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp)); + // The grace period cannot end while we hold the rcu_node lock. + if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) + WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp)); raw_spin_unlock_rcu_node(rnp); } -- 2.20.1