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rcu: Document reason for rcu_all_qs() call to preempt_disable()

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Given that rcu_all_qs() is in non-preemptible kernels, why on earth should
it invoke preempt_disable()?  This commit adds the reason, which is to
work nicely with debugging enabled in CONFIG_PREEMPT_COUNT=y kernels.

Reported-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-08-03 08:48:12 -07:00
parent 6ca0292ccf
commit 089254fd38
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tree_plugin.h
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@ -870,7 +870,7 @@ void rcu_all_qs(void)
if (!raw_cpu_read(rcu_data.rcu_urgent_qs))
return;
preempt_disable();
preempt_disable(); // For CONFIG_PREEMPT_COUNT=y kernels
/* Load rcu_urgent_qs before other flags. */
if (!smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
preempt_enable();