linux-kernel - [PATCH] rcu/exp: Fix check for idle context in rcu_exp

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Message-ID: <20211213061024.24285-1-quic_neeraju@quicinc.com>
Date:   Mon, 13 Dec 2021 11:40:24 +0530
From:   Neeraj Upadhyay <quic_neeraju@...cinc.com>
To:     <paulmck@...nel.org>, <josh@...htriplett.org>,
        <rostedt@...dmis.org>, <mathieu.desnoyers@...icios.com>,
        <jiangshanlai@...il.com>, <joel@...lfernandes.org>
CC:     <rcu@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <urezki@...il.com>, <frederic@...nel.org>, <boqun.feng@...il.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>
Subject: [PATCH] rcu/exp: Fix check for idle context in rcu_exp_handler

For PREEMPT_RCU, the rcu_exp_handler() function checks
whether the current CPU is in idle, by calling
rcu_dynticks_curr_cpu_in_eqs(). However, rcu_exp_handler()
is called in IPI handler context. So, it should be checking
the idle context using rcu_is_cpu_rrupt_from_idle(). Fix this
by using rcu_is_cpu_rrupt_from_idle() instead of
rcu_dynticks_curr_cpu_in_eqs(). Non-preempt configuration
already uses the correct check.

Signed-off-by: Neeraj Upadhyay <quic_neeraju@...cinc.com>
---
 kernel/rcu/tree_exp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 237a79989aba..1568c8ef185b 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -656,7 +656,7 @@ static void rcu_exp_handler(void *unused)
 	 */
 	if (!depth) {
 		if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
-		    rcu_dynticks_curr_cpu_in_eqs()) {
+		    rcu_is_cpu_rrupt_from_idle()) {
 			rcu_report_exp_rdp(rdp);
 		} else {
 			WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);
-- 
2.17.1