From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
rostedt@goodmis.org, Kunwu Chan <kunwu.chan@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Bradley Morgan <brads@mainlining.org>
Subject: [PATCH 18/19] srcutree: Don't transition atomic SRCU to big in srcu_gp_end()
Date: Fri, 18 Sep 2026 17:35:20 -0700 [thread overview]
Message-ID: <20260919003521.3134552-18-paulmck@kernel.org> (raw)
In-Reply-To: <13d6be93-8d9d-47a2-beb0-99c8a90938d4@paulmck-laptop>
From: Kunwu Chan <kunwu.chan@gmail.com>
Atomic SRCU must remain in the small size state. Warn if this
invariant is violated and avoid transitioning to big in that case.
[ paulmck: Folded "if" onto one line for 100-character limit. ]
Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
---
kernel/rcu/srcutree.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 4e9a0b8ea344..6a05bd8a6f39 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1073,8 +1073,10 @@ 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
--
2.40.1
next prev parent reply other threads:[~2026-09-19 0:35 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-19 0:35 [PATCH 0/19] Add atomic SRCU Paul E. McKenney
2026-09-19 0:35 ` [PATCH 01/19] srcutiny: Make a Tiny SRCU grace period imply an RCU grace period Paul E. McKenney
2026-09-19 0:35 ` [PATCH 02/19] srcutree: Suppress srcu_advance_state() mutex_lock in atomic Paul E. McKenney
2026-09-19 0:35 ` [PATCH 03/19] srcutree: Suppress to-big transition for atomic SRCU Paul E. McKenney
2026-09-19 0:35 ` [PATCH 04/19] srcutree: Add an atomic Tree SRCU Paul E. McKenney
2026-09-19 0:35 ` [PATCH 05/19] srcutiny: Add an atomic Tiny SRCU Paul E. McKenney
2026-09-19 0:35 ` [PATCH 06/19] rcutorture: Add support for testing synchronize_srcu_atomic() Paul E. McKenney
2026-09-19 0:35 ` [PATCH 07/19] srcutree: Disable preemption across synchronize_srcu_atomic() Paul E. McKenney
2026-09-19 0:35 ` [PATCH 08/19] srcu: Use IRQ_WORK_INIT_HARD for srcu's irq_work Paul E. McKenney
2026-09-19 0:35 ` [PATCH 09/19] srcu: Fix WARN_ON() for rcu_segcblist_n_cbs() in cleanup_srcu_struct() Paul E. McKenney
2026-10-01 0:27 ` Sean Christopherson
2026-10-01 0:57 ` Paul E. McKenney
2026-10-02 0:27 ` Paul E. McKenney
2026-09-19 0:35 ` [PATCH 10/19] srcutree: Warn if Tiny SRCU readers are preempted Paul E. McKenney
2026-09-19 0:35 ` [PATCH 11/19] srcutree: Explicitly note DEFINE_SRCU() needs for srcu_barrier() Paul E. McKenney
2026-09-19 0:35 ` [PATCH 12/19] rcutorture: Add atomic-SRCU support to torture.sh Paul E. McKenney
2026-09-19 0:35 ` [PATCH 13/19] srcutree: Add reader-free fastpath to synchronize_srcu_atomic() Paul E. McKenney
2026-09-19 0:35 ` [PATCH 14/19] srcutree: Skip callback scheduling for atomic SRCU grace periods Paul E. McKenney
2026-09-19 0:35 ` [PATCH 15/19] srcutree: Remove srcu_barrier() sleep for atomic SRCU Paul E. McKenney
2026-09-19 0:35 ` [PATCH 16/19] srcu: Restrict atomic-SRCU non_block annotation to task context Paul E. McKenney
2026-09-19 0:35 ` [PATCH 17/19] srcutree: Make init_srcu_struct_atomic() prevent transition to big Paul E. McKenney
2026-09-19 0:35 ` Paul E. McKenney [this message]
2026-09-19 0:35 ` [PATCH 19/19] srcutree: Skip torture to-big transition for atomic SRCU Paul E. McKenney
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