From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
rostedt@goodmis.org, Frederic Weisbecker <frederic@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH v3 rcu 10/11] srcu: Explain the reason behind the read side critical section on GP start
Date: Wed, 19 Oct 2022 15:58:45 -0700 [thread overview]
Message-ID: <20221019225846.2501109-10-paulmck@kernel.org> (raw)
In-Reply-To: <20221019225838.GA2500612@paulmck-ThinkPad-P17-Gen-1>
From: Frederic Weisbecker <frederic@kernel.org>
Tell about the need to protect against concurrent updaters who may
overflow the GP counter behind the current update.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/srcutree.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 18bb696cff8ca..272830a87e566 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1158,6 +1158,11 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
int ss_state;
check_init_srcu_struct(ssp);
+ /*
+ * While starting a new grace period, make sure we are in an
+ * SRCU read-side critical section so that the grace-period
+ * sequence number cannot wrap around in the meantime.
+ */
idx = __srcu_read_lock_nmisafe(ssp, false);
ss_state = smp_load_acquire(&ssp->srcu_size_state);
if (ss_state < SRCU_SIZE_WAIT_CALL)
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2022-10-19 22:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 22:58 [PATCH rcu 0/11] NMI-safe SRCU readers for v6.2 Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 01/11] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 02/11] srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 03/11] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 04/11] srcu: Check for consistent global " Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 05/11] arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 06/11] arch/arm64: " Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 07/11] arch/loongarch: " Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 08/11] arch/s390: " Paul E. McKenney
2022-10-20 5:16 ` Christian Borntraeger
2022-10-20 7:23 ` Heiko Carstens
2022-10-20 7:27 ` Heiko Carstens
2022-10-20 16:35 ` Paul E. McKenney
2022-10-19 22:58 ` [PATCH v3 rcu 09/11] srcu: Warn when NMI-unsafe API is used in NMI Paul E. McKenney
2022-10-19 22:58 ` Paul E. McKenney [this message]
2022-10-19 22:58 ` [PATCH v3 rcu 11/11] srcu: Debug NMI safety even on archs that don't require it Paul E. McKenney
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