linux-kernel - [PATCH] srcu: Add detection of boot CPU srcu_data structure's->srcu

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Date:   Thu, 17 Nov 2022 19:20:50 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org, joel@...lfernandes.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] srcu: Add detection of boot CPU srcu_data structure's->srcu_cblist

Before SRCU_SIZE_WAIT_CALL srcu_size_state is reached, the srcu
callback only insert to boot-CPU srcu_data structure's->srcu_cblist
and other CPU srcu_data structure's->srcu_cblist is always empty. so
before SRCU_SIZE_WAIT_CALL is reached, need to correctly check boot-CPU
pend cbs in srcu_might_be_idle().

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 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 6af031200580..6d9af9901765 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1098,8 +1098,11 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp)
 	unsigned long tlast;
 
 	check_init_srcu_struct(ssp);
-	/* If the local srcu_data structure has callbacks, not idle.  */
-	sdp = raw_cpu_ptr(ssp->sda);
+	/* If the boot CPU or local srcu_data structure has callbacks, not idle.  */
+	if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_CALL)
+		sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
+	else
+		sdp = raw_cpu_ptr(ssp->sda);
 	spin_lock_irqsave_rcu_node(sdp, flags);
 	if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) {
 		spin_unlock_irqrestore_rcu_node(sdp, flags);
-- 
2.25.1