From: "Paul E. McKenney" paulmck@kernel.org

[ Upstream commit a24c1aab652ebacf9ea62470a166514174c96fe1 ]

The rcu_data structure's ->rcu_cpu_has_work field can be modified by any CPU attempting to wake up the rcuc kthread. Therefore, this commit marks accesses to this field from the rcu_cpu_kthread() function.

This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely.

Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/rcu/tree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index eec8e2f7537eb..b2c1ab260ed56 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2810,12 +2810,12 @@ static void rcu_cpu_kthread(unsigned int cpu) *statusp = RCU_KTHREAD_RUNNING; local_irq_disable(); work = *workp; - *workp = 0; + WRITE_ONCE(*workp, 0); local_irq_enable(); if (work) rcu_core(); local_bh_enable(); - if (*workp == 0) { + if (!READ_ONCE(*workp)) { trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); *statusp = RCU_KTHREAD_WAITING; return;