Atomic SRCU must remain in the small size state. Warn if this invariant is violated and avoid transitioning to big in that case.
Signed-off-by: Kunwu Chan <[email protected]> --- Changes since v2: - Also prevent the transition when the atomic SRCU size-state invariant is violated, per Paul McKenney's suggestion. -v2: https://lore.kernel.org/rcu/[email protected]/ Changes since v1: - Drop the !is_atomic guard from v1 and add WARN_ON_ONCE() instead, per Paul McKenney's suggestion. - v1: https://lore.kernel.org/rcu/[email protected]/ --- kernel/rcu/srcutree.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 84c022ec8e09..07db4e459b30 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1073,8 +1073,11 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic) raw_spin_unlock_irq_rcu_node(sup); } - /* Transition to big if needed. */ - if (ss_state != SRCU_SIZE_SMALL && ss_state != SRCU_SIZE_BIG) { + /* Transition to big if needed, but never for atomic SRCU. */ + if (ssp->srcu_reader_flavor == SRCU_READ_FLAVOR_ATOMIC && + ss_state != SRCU_SIZE_SMALL) { + WARN_ON_ONCE(1); + } else if (ss_state != SRCU_SIZE_SMALL && ss_state != SRCU_SIZE_BIG) { if (ss_state == SRCU_SIZE_ALLOC) init_srcu_struct_nodes(ssp, GFP_KERNEL); else -- 2.43.0
