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rcu: Suppress smp_processor_id() complaint in synchronize_rcu_expedited_wait()

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The normal grace period's RCU CPU stall warnings are invoked from the
scheduling-clock interrupt handler, and can thus invoke smp_processor_id()
with impunity, which allows them to directly invoke dump_cpu_task().
In contrast, the expedited grace period's RCU CPU stall warnings are
invoked from process context, which causes the dump_cpu_task() function's
calls to smp_processor_id() to complain bitterly in debug kernels.

This commit therefore causes synchronize_rcu_expedited_wait() to disable
preemption around its call to dump_cpu_task().

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-12-16 15:55:48 -08:00
parent 0cae5ded53
commit 2d7f00b2f0
1 changed files with 2 additions and 0 deletions
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2
kernel/rcu/tree_exp.h
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@ -667,7 +667,9 @@ static void synchronize_rcu_expedited_wait(void)
mask = leaf_node_cpu_bit(rnp, cpu); mask = leaf_node_cpu_bit(rnp, cpu);
if (!(READ_ONCE(rnp->expmask) & mask)) if (!(READ_ONCE(rnp->expmask) & mask))
continue; continue;
preempt_disable(); // For smp_processor_id() in dump_cpu_task().
dump_cpu_task(cpu); dump_cpu_task(cpu);
preempt_enable();
} }
} }
jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3; jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;