Messages in this thread | | | Subject | Re: [PATCH 04/11] rcu: cleanup rcu_preempt_deferred_qs() | From | Lai Jiangshan <> | Date | Thu, 31 Oct 2019 22:35:22 +0800 |
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On 2019/10/31 10:10 下午, Paul E. McKenney wrote: > On Thu, Oct 31, 2019 at 10:07:59AM +0000, Lai Jiangshan wrote: >> Don't need to set ->rcu_read_lock_nesting negative, irq-protected >> rcu_preempt_deferred_qs_irqrestore() doesn't expect >> ->rcu_read_lock_nesting to be negative to work, it even >> doesn't access to ->rcu_read_lock_nesting any more. >> >> It is true that NMI over rcu_preempt_deferred_qs_irqrestore() >> may access to ->rcu_read_lock_nesting, but it is still safe >> since rcu_read_unlock_special() can protect itself from NMI. > > Hmmm... Testing identified the need for this one. But I will wait for > your responses on the earlier patches before going any further through > this series.
Hmmm... I was wrong, it should be after patch7 to avoid the scheduler deadlock.
> > Thanx, Paul > >> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> >> --- >> kernel/rcu/tree_plugin.h | 5 ----- >> 1 file changed, 5 deletions(-) >> >> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h >> index 82595db04eec..9fe8138ed3c3 100644 >> --- a/kernel/rcu/tree_plugin.h >> +++ b/kernel/rcu/tree_plugin.h >> @@ -555,16 +555,11 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) >> static void rcu_preempt_deferred_qs(struct task_struct *t) >> { >> unsigned long flags; >> - bool couldrecurse = t->rcu_read_lock_nesting >= 0; >> >> if (!rcu_preempt_need_deferred_qs(t)) >> return; >> - if (couldrecurse) >> - t->rcu_read_lock_nesting -= RCU_NEST_BIAS; >> local_irq_save(flags); >> rcu_preempt_deferred_qs_irqrestore(t, flags); >> - if (couldrecurse) >> - t->rcu_read_lock_nesting += RCU_NEST_BIAS; >> } >> >> /* >> -- >> 2.20.1 >>
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