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    SubjectRe: [PATCH] sched/core: add rcu_read_lock/unlock() protection
    On Tue, Jan 26, 2021 at 04:46:51PM +0800, qiang.zhang@windriver.com wrote:
    > From: Zqiang <qiang.zhang@windriver.com>
    >
    > Due to for_each_process_thread belongs to RCU read operation,
    > need to add rcu_read_lock/unlock() protection.
    >
    > Signed-off-by: Zqiang <qiang.zhang@windriver.com>
    > ---
    > kernel/sched/core.c | 2 ++
    > 1 file changed, 2 insertions(+)
    >
    > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    > index 8c5481077c9c..c3f0103fdf53 100644
    > --- a/kernel/sched/core.c
    > +++ b/kernel/sched/core.c
    > @@ -7738,6 +7738,7 @@ static void dump_rq_tasks(struct rq *rq, const char *loglvl)
    > lockdep_assert_held(&rq->lock);
    >
    > printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
    > + rcu_read_lock();
    > for_each_process_thread(g, p) {
    > if (task_cpu(p) != cpu)
    > continue;
    > @@ -7747,6 +7748,7 @@ static void dump_rq_tasks(struct rq *rq, const char *loglvl)
    >
    > printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
    > }
    > + rcu_read_unlock();

    We're in stop machine, with IRQs disabled, please explain how this can
    make any difference?

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