linux-kernel - [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code

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Message-Id: <20221013044148.2894320-1-qiang1.zhang@intel.com>
Date:   Thu, 13 Oct 2022 12:41:48 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        joel@...lfernandes.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code

BUG: using __this_cpu_read() in preemptible [00000000]
code: rcu_torture_fqs/398
caller is __this_cpu_preempt_check+0x13/0x20
CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x86
dump_stack+0x10/0x16
check_preemption_disabled+0xe5/0xf0
__this_cpu_preempt_check+0x13/0x20
rcu_force_quiescent_state.part.0+0x1c/0x170
rcu_force_quiescent_state+0x1e/0x30
rcu_torture_fqs+0xca/0x160
? rcu_torture_boost+0x430/0x430
kthread+0x192/0x1d0
? kthread_complete_and_exit+0x30/0x30
ret_from_fork+0x22/0x30
</TASK>

When enable rcutorture.fqs_duration, the rcu_force_quiescent_state() be
invoked in rcu_torture_fqs task context, invoke __this_cpu_read() in
preemptible code section will trigger the above calltrace.

This commit convert __this_cpu_read() to raw_cpu_read() to avoid
this warning.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 96d678c9cfb6..282002e62cf3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2436,7 +2436,7 @@ void rcu_force_quiescent_state(void)
 	struct rcu_node *rnp_old = NULL;

 	/* Funnel through hierarchy to reduce memory contention. */
-	rnp = __this_cpu_read(rcu_data.mynode);
+	rnp = raw_cpu_read(rcu_data.mynode);
 	for (; rnp != NULL; rnp = rnp->parent) {
 		ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
 		       !raw_spin_trylock(&rnp->fqslock);
-- 
2.25.1