rcu: Let dump_cpu_task() be used without preemption disabled
The commit 2d7f00b2f0130 ("rcu: Suppress smp_processor_id() complaint
in synchronize_rcu_expedited_wait()") disabled preemption around
dump_cpu_task() to suppress warning on its usage within preemtible context.
Calling dump_cpu_task() doesn't required to be in non-preemptible context
except for suppressing the smp_processor_id() warning.
As the smp_processor_id() is evaluated along with in_hardirq()
to check if it's in interrupt context, this patch removes the need
for its preemtion disablement by reordering the condition so that
smp_processor_id() only gets evaluated when it's in interrupt context.
Signed-off-by: Ryo Takakura <takakura@valinux.co.jp>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index d4be644..c5d9a7e 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -597,9 +597,7 @@ static void synchronize_rcu_expedited_stall(unsigned long jiffies_start, unsigne
mask = leaf_node_cpu_bit(rnp, cpu);
if (!(READ_ONCE(rnp->expmask) & mask))
continue;
- preempt_disable(); // For smp_processor_id() in dump_cpu_task().
dump_cpu_task(cpu);
- preempt_enable();
}
rcu_exp_print_detail_task_stall_rnp(rnp);
}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 05afa29..bdb0e03 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11485,7 +11485,7 @@ struct cgroup_subsys cpu_cgrp_subsys = {
void dump_cpu_task(int cpu)
{
- if (cpu == smp_processor_id() && in_hardirq()) {
+ if (in_hardirq() && cpu == smp_processor_id()) {
struct pt_regs *regs;
regs = get_irq_regs();
