Re: [PATCH 2/6] xen: add helper for calling notifier_call_chain() to common/cpu.c

From: Juergen Gross <jgross@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Tim Deegan <tim@xen.org>, Ian Jackson <ian.jackson@eu.citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH 2/6] xen: add helper for calling notifier_call_chain() to common/cpu.c
Date: Wed, 27 Mar 2019 17:05:06 +0100	[thread overview]
Message-ID: <02fbc23c-b7db-5595-829d-b79e561e76db@suse.com> (raw)
In-Reply-To: <442ec458-d00e-251f-e206-d6d392f334ed@citrix.com>

On 27/03/2019 16:39, Andrew Cooper wrote:
> On 18/03/2019 13:11, Juergen Gross wrote:
>> Add a helper cpu_notifier_call_chain() to call notifier_call_chain()
>> for a cpu with a specified action, returning an errno value.
>>
>> This avoids coding the same pattern multiple times.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>  xen/common/cpu.c | 50 +++++++++++++++++++++-----------------------------
>>  1 file changed, 21 insertions(+), 29 deletions(-)
>>
>> diff --git a/xen/common/cpu.c b/xen/common/cpu.c
>> index 836c62f97f..c436c0de7f 100644
>> --- a/xen/common/cpu.c
>> +++ b/xen/common/cpu.c
>> @@ -71,11 +71,18 @@ void __init register_cpu_notifier(struct notifier_block *nb)
>>      spin_unlock(&cpu_add_remove_lock);
>>  }
>>  
>> +static int cpu_notifier_call_chain(unsigned int cpu, unsigned long action,
>> +                                   struct notifier_block **nb)
>> +{
>> +    void *hcpu = (void *)(long)cpu;
>> +    int notifier_rc = notifier_call_chain(&cpu_chain, action, hcpu, nb);
>> +
>> +    return (notifier_rc == NOTIFY_DONE) ? 0 : notifier_to_errno(notifier_rc);
>> +}
>> +
>>  static void _take_cpu_down(void *unused)
>>  {
>> -    void *hcpu = (void *)(long)smp_processor_id();
>> -    int notifier_rc = notifier_call_chain(&cpu_chain, CPU_DYING, hcpu, NULL);
>> -    BUG_ON(notifier_rc != NOTIFY_DONE);
>> +    BUG_ON(cpu_notifier_call_chain(smp_processor_id(), CPU_DYING, NULL));
> 
> Where possible, we're trying to remove side effects from macros.
> 
> Could I please talk you into writing this as:
> 
> int rc = cpu_notifier_call_chain(smp_processor_id(), CPU_DYING, NULL);
> 
> BUG_ON(rc);

Fine with me.

Juergen

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