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Re: [PATCH] xen/smp: Support NULL IPI function pointers
- To: Wei Chen <Wei.Chen@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 18 Nov 2021 10:56:04 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Delivery-date: Thu, 18 Nov 2021 09:56:21 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.11.2021 07:51, Wei Chen wrote:
> On 2021/11/18 0:48, Andrew Cooper wrote:
>> --- a/xen/common/smp.c
>> +++ b/xen/common/smp.c
>> @@ -87,10 +87,14 @@ void smp_call_function_interrupt(void)
>>
>> irq_enter();
>>
>> + if ( unlikely(!func) )
>> + goto no_func;
>> +
>> if ( call_data.wait )
>> {
>> (*func)(info);
>> smp_mb();
>> + no_func:
>> cpumask_clear_cpu(cpu, &call_data.selected);
>> }
>> else
>
> Why only apply to call_data.wait non-zero case?
> Is it because func will not be NULL when call_data.wait is zero?
No. call_data.wait is irrelevant when no function is to be called.
If you look at the "else" branch, all that would be needed there
is again just the cpumask_clear_cpu() invocation. Hence easiest to
wire it like Andrew did (leaving aside my personal dislike of goto).
Jan
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