linux-kernel - Re: [PATCH] x86/acpi: Fix a warning message in logical CPU IDs allocation

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Date:   Wed, 1 Mar 2017 10:10:07 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
Cc:     tglx@...utronix.de, hpa@...or.com, bp@...en8.de,
        wanpeng.li@...mail.com, nicstange@...il.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/acpi: Fix a warning message in logical CPU IDs
 allocation


* Dou Liyang <douly.fnst@...fujitsu.com> wrote:

> Current warning message regarded the "nr_cpu_ids - 1" as the limit
> number of the CPUs. It may be confused us, for example:
> we have two CPUs, nr_cpu_ids = 2, but the warning message may
> indicate that we just have 1 CPU, which likes that:
>     Only 1 processors supported.Processor 2/0x2 and the rest
>     are ignored.
> 
> Fix the warning message, replace "nr_cpu_ids - 1" with "nr_cpu_ids".
> And the warning message can be like that:
>     APIC: NR_CPUS/possible_cpus limit of 2 reached. Processor 2/0x2
>     and the rest are ignored.
> 
> Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>

The patch is correct, but the title is wrong (it's 'apic', not 'acpi'), plus the 
changelog is unreadable. Furthermore the changelog does not declare the changing 
of the return code to -EINVAL ...

I fixed all that in the commit below, but please be more careful in the future.

Thanks,

	Ingo

=======================>
>From bb3f0a52630c84807fca9bdd76ac2f5dcec82689 Mon Sep 17 00:00:00 2001
From: Dou Liyang <douly.fnst@...fujitsu.com>
Date: Tue, 28 Feb 2017 13:50:52 +0800
Subject: [PATCH] x86/apic: Fix a warning message in logical CPU IDs allocation

The current warning message in allocate_logical_cpuid() is somewhat confusing:

  Only 1 processors supported.Processor 2/0x2 and the rest are ignored.

As it might imply that there's only one CPU in the system - while what we ran
into here is a kernel limitation.

Fix the warning message to clarify all that:

  APIC: NR_CPUS/possible_cpus limit of 2 reached. Processor 2/0x2 and the rest are ignored.

( Also update the error return from -1 to -EINVAL, which is the more
  canonical return value. )

Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: bp@...en8.de
Cc: nicstange@...il.com
Cc: wanpeng.li@...mail.com
Link: http://lkml.kernel.org/r/1488261052-25753-1-git-send-email-douly.fnst@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/apic/apic.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 4261b3282ad9..11088b86e5c7 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2062,10 +2062,10 @@ static int allocate_logical_cpuid(int apicid)
 
 	/* Allocate a new cpuid. */
 	if (nr_logical_cpuids >= nr_cpu_ids) {
-		WARN_ONCE(1, "Only %d processors supported."
+		WARN_ONCE(1, "APIC: NR_CPUS/possible_cpus limit of %i reached. "
 			     "Processor %d/0x%x and the rest are ignored.\n",
-			     nr_cpu_ids - 1, nr_logical_cpuids, apicid);
-		return -1;
+			     nr_cpu_ids, nr_logical_cpuids, apicid);
+		return -EINVAL;
 	}
 
 	cpuid_to_apicid[nr_logical_cpuids] = apicid;