linux-kernel - Re: [PATCH] sched/deadline: Test for CPU's presence explicitly

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Message-ID: <53022F86.2080204@gmail.com>
Date:	Mon, 17 Feb 2014 16:49:26 +0100
From:	Juri Lelli <juri.lelli@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	konrad.wilk@...cle.com
Subject: Re: [PATCH] sched/deadline: Test for CPU's presence explicitly

On 02/17/2014 03:50 PM, Peter Zijlstra wrote:
> On Mon, Feb 17, 2014 at 09:12:33AM -0500, Boris Ostrovsky wrote:
>> A hot-removed CPU may have ID that is numerically larger than the number of
>> existing CPUs in the system (e.g. we can unplug CPU 4 from a system that
>> has CPUs 0, 1 and 4).
>>
>> Thus the WARN_ONs should check whether the CPU in question is currently
>> present, not whether its ID value is less than num_present_cpus().
>>
>> Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> 
> Thanks!, please also always CC the author of the code in question.
>

Thanks!

- Juri

>> ---
>>  kernel/sched/cpudeadline.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>> index 045fc74..5b8838b 100644
>> --- a/kernel/sched/cpudeadline.c
>> +++ b/kernel/sched/cpudeadline.c
>> @@ -70,7 +70,7 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
>>  
>>  static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
>>  {
>> -	WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
>> +	WARN_ON(!cpu_present(idx) || idx == IDX_INVALID);
>>  
>>  	if (dl_time_before(new_dl, cp->elements[idx].dl)) {
>>  		cp->elements[idx].dl = new_dl;
>> @@ -117,7 +117,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>>  	}
>>  
>>  out:
>> -	WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
>> +	WARN_ON(!cpu_present(best_cpu) && best_cpu != -1);
>>  
>>  	return best_cpu;
>>  }
>> @@ -137,7 +137,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
>>  	int old_idx, new_cpu;
>>  	unsigned long flags;
>>  
>> -	WARN_ON(cpu > num_present_cpus());
>> +	WARN_ON(!cpu_present(cpu));
>>  
>>  	raw_spin_lock_irqsave(&cp->lock, flags);
>>  	old_idx = cp->cpu_to_idx[cpu];
>> -- 
>> 1.8.1.4
>>
--
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