linux-kernel - Re: [PATCH 6/7] rcu: rename some CONFIG_PREEMPTION to CONFIG_PREEMPT

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Date:   Wed, 16 Oct 2019 23:26:23 +0800
From:   Lai Jiangshan <laijs@...ux.alibaba.com>
To:     paulmck@...nel.org, 20191015102402.1978-1-laijs@...ux.alibaba.com
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org
Subject: Re: [PATCH 6/7] rcu: rename some CONFIG_PREEMPTION to
 CONFIG_PREEMPT_RCU



On 2019/10/16 11:54 上午, Paul E. McKenney wrote:
> On Tue, Oct 15, 2019 at 10:28:48AM +0000, Lai Jiangshan wrote:
>> CONFIG_PREEMPTION and CONFIG_PREEMPT_RCU are always identical,
>> but some code depends on CONFIG_PREEMPTION to access to
>> rcu_preempt functionalitis. This patch changes CONFIG_PREEMPTION
>> to CONFIG_PREEMPT_RCU in these cases.
>>
>> Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
>> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> 
> I believe that this does not cause problems with Sebastian's patch
> "[PATCH 27/34] rcu: Use CONFIG_PREEMPTION where appropriate", but could
> you please check?

I don't know for which commit the patch "[PATCH 27/34] rcu: Use
CONFIG_PREEMPTION where appropriate" should be applied against
after several tries. But I don't think there will be any conflicts
which this patch by "eye" applying.

Thanks,
Lai



> 
> 							Thanx, Paul
> 
>> ---
>>   kernel/rcu/tree.c       | 4 ++--
>>   kernel/rcu/tree_stall.h | 6 +++---
>>   2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
>> index 7db5ea06a9ed..81eb64fcf5ab 100644
>> --- a/kernel/rcu/tree.c
>> +++ b/kernel/rcu/tree.c
>> @@ -1926,7 +1926,7 @@ rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
>>   	struct rcu_node *rnp_p;
>>   
>>   	raw_lockdep_assert_held_rcu_node(rnp);
>> -	if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPTION)) ||
>> +	if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_RCU)) ||
>>   	    WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
>>   	    rnp->qsmask != 0) {
>>   		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
>> @@ -2294,7 +2294,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
>>   		mask = 0;
>>   		raw_spin_lock_irqsave_rcu_node(rnp, flags);
>>   		if (rnp->qsmask == 0) {
>> -			if (!IS_ENABLED(CONFIG_PREEMPTION) ||
>> +			if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
>>   			    rcu_preempt_blocked_readers_cgp(rnp)) {
>>   				/*
>>   				 * No point in scanning bits because they
>> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
>> index 0b75426ebb3e..55f9b84790d3 100644
>> --- a/kernel/rcu/tree_stall.h
>> +++ b/kernel/rcu/tree_stall.h
>> @@ -163,7 +163,7 @@ static void rcu_iw_handler(struct irq_work *iwp)
>>   //
>>   // Printing RCU CPU stall warnings
>>   
>> -#ifdef CONFIG_PREEMPTION
>> +#ifdef CONFIG_PREEMPT_RCU
>>   
>>   /*
>>    * Dump detailed information for all tasks blocking the current RCU
>> @@ -215,7 +215,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
>>   	return ndetected;
>>   }
>>   
>> -#else /* #ifdef CONFIG_PREEMPTION */
>> +#else /* #ifdef CONFIG_PREEMPT_RCU */
>>   
>>   /*
>>    * Because preemptible RCU does not exist, we never have to check for
>> @@ -233,7 +233,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
>>   {
>>   	return 0;
>>   }
>> -#endif /* #else #ifdef CONFIG_PREEMPTION */
>> +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
>>   
>>   /*
>>    * Dump stacks of all tasks running on stalled CPUs.  First try using
>> -- 
>> 2.20.1
>>