Re: [PATCH v4 04/12] smp: Use task-local IPI cpumask in smp_call_function_many_cond()

[Chuyi Zhou]

On 2026-04-01 11:25 p.m., Sebastian Andrzej Siewior wrote:
> On 2026-03-31 19:30:55 [+0800], Chuyi Zhou wrote:
> 
>> --- a/kernel/smp.c
>> +++ b/kernel/smp.c
>> @@ -802,11 +840,18 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
>>   	int cpu, last_cpu, this_cpu = smp_processor_id();
>>   	struct call_function_data *cfd;
>>   	bool wait = scf_flags & SCF_WAIT;
>> +	struct cpumask *cpumask, *task_mask;
>> +	bool preemptible_wait;
>>   	int nr_cpus = 0;
>>   	bool run_remote = false;
>>   
>>   	lockdep_assert_preemption_disabled();
>>   
>> +	task_mask = smp_task_ipi_mask(current);
>> +	preemptible_wait = task_mask && preemptible();
>> +	cfd = this_cpu_ptr(&cfd_data);
>> +	cpumask = preemptible_wait ? task_mask : cfd->cpumask;
> 
> I haven't look at this in detail but that
> lockdep_assert_preemption_disabled() expects preemption to be disabled
> here so the following preemptible() must be always false.
> 

Yes, perhaps the preemptible() check is not needed in this patch.

It would be better to add the preemptible() check in [patch 06/12].

>> +
>>   	/*
>>   	 * Can deadlock when called with interrupts disabled.
>>   	 * We allow cpu's that are not yet online though, as no one else can
> 
> Sebastian