linux-kernel - Re: [PATCH] x86: cleanups to nmi

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Date:	Mon, 9 Jun 2008 00:28:19 +0400
From:	"Cyrill Gorcunov" <gorcunov@...il.com>
To:	"Németh Márton" <nm127@...email.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: cleanups to nmi_watchdog variable

Btw, if you interested to clean it up (which means not cleanup in real
:) i suggest to analize _if_ there is benefit from sign changing. Mark
that -1 is the 0xff... form of presentation for unsigned type. And
thanks for catching this. It defenitely should be simplified once.

On 6/8/08, Németh Márton <nm127@...email.hu> wrote:
> Cyrill Gorcunov wrote:
>> | From: Márton Németh <nm127@...email.hu>
>> |
>> | Use NMI_NONE instead of 0. As the symbol NMI_DISABLED equals to -1,
>> | the nmi_watchdog variable should also be signed.
>> |
>> | Signed-off-by: Márton Németh <nm127@...email.hu>
>> | ---
>> | diff -upr linux-2.6.26-rc5.orig/arch/x86/kernel/io_apic_32.c
>> linux-2.6.26-rc5/arch/x86/kernel/io_apic_32.c
>> | --- linux-2.6.26-rc5.orig/arch/x86/kernel/io_apic_32.c	2008-06-07
>> 12:35:24.000000000 +0200
>> | +++ linux-2.6.26-rc5/arch/x86/kernel/io_apic_32.c	2008-06-07
>> 12:40:20.000000000 +0200
>> | @@ -2217,7 +2217,7 @@ static inline void __init check_timer(vo
>> |
>> |  	if (nmi_watchdog == NMI_IO_APIC) {
>> |  		printk(KERN_WARNING "timer doesn't work through the IO-APIC -
>> disabling NMI Watchdog!\n");
>> | -		nmi_watchdog = 0;
>> | +		nmi_watchdog = NMI_NONE;
>> |  	}
>> |
>> |  	printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");
>> | diff -upr linux-2.6.26-rc5.orig/arch/x86/kernel/io_apic_64.c
>> linux-2.6.26-rc5/arch/x86/kernel/io_apic_64.c
>> | --- linux-2.6.26-rc5.orig/arch/x86/kernel/io_apic_64.c	2008-06-05
>> 18:39:49.000000000 +0200
>> | +++ linux-2.6.26-rc5/arch/x86/kernel/io_apic_64.c	2008-06-07
>> 12:37:01.000000000 +0200
>> | @@ -1735,7 +1735,7 @@ static inline void __init check_timer(vo
>> |
>> |  	if (nmi_watchdog == NMI_IO_APIC) {
>> |  		printk(KERN_WARNING "timer doesn't work through the IO-APIC -
>> disabling NMI Watchdog!\n");
>> | -		nmi_watchdog = 0;
>> | +		nmi_watchdog = NMI_NONE;
>> |  	}
>> |
>> |  	apic_printk(APIC_VERBOSE, KERN_INFO "...trying to set up timer as
>> Virtual Wire IRQ...");
>> | diff -upr linux-2.6.26-rc5.orig/arch/x86/kernel/nmi_32.c
>> linux-2.6.26-rc5/arch/x86/kernel/nmi_32.c
>> | --- linux-2.6.26-rc5.orig/arch/x86/kernel/nmi_32.c	2008-06-05
>> 18:39:49.000000000 +0200
>> | +++ linux-2.6.26-rc5/arch/x86/kernel/nmi_32.c	2008-06-07
>> 11:19:55.000000000 +0200
>> | @@ -43,7 +43,7 @@ static cpumask_t backtrace_mask = CPU_MA
>> |   */
>> |  atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
>> |
>> | -unsigned int nmi_watchdog = NMI_DEFAULT;
>> | +int nmi_watchdog = NMI_DEFAULT;
>> |  static unsigned int nmi_hz = HZ;
>> |
>> |  static DEFINE_PER_CPU(short, wd_enabled);
>> | diff -upr linux-2.6.26-rc5.orig/arch/x86/kernel/nmi_64.c
>> linux-2.6.26-rc5/arch/x86/kernel/nmi_64.c
>> | --- linux-2.6.26-rc5.orig/arch/x86/kernel/nmi_64.c	2008-06-05
>> 18:39:49.000000000 +0200
>> | +++ linux-2.6.26-rc5/arch/x86/kernel/nmi_64.c	2008-06-07
>> 11:20:00.000000000 +0200
>> | @@ -43,7 +43,7 @@ static cpumask_t backtrace_mask = CPU_MA
>> |  atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
>> |  static int panic_on_timeout;
>> |
>> | -unsigned int nmi_watchdog = NMI_DEFAULT;
>> | +int nmi_watchdog = NMI_DEFAULT;
>> |  static unsigned int nmi_hz = HZ;
>> |
>> |  static DEFINE_PER_CPU(short, wd_enabled);
>> | diff -upr linux-2.6.26-rc5.orig/include/asm-x86/nmi.h
>> linux-2.6.26-rc5/include/asm-x86/nmi.h
>> | --- linux-2.6.26-rc5.orig/include/asm-x86/nmi.h	2008-06-05
>> 18:40:12.000000000 +0200
>> | +++ linux-2.6.26-rc5/include/asm-x86/nmi.h	2008-06-07 11:21:20.000000000
>> +0200
>> | @@ -61,7 +61,7 @@ extern void enable_timer_nmi_watchdog(vo
>> |  extern int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason);
>> |
>> |  extern atomic_t nmi_active;
>> | -extern unsigned int nmi_watchdog;
>> | +extern int nmi_watchdog;
>> |  #define NMI_DISABLED    -1
>> |  #define NMI_NONE	0
>> |  #define NMI_IO_APIC	1
>> |
>>
>> We should leave nmi_watchdog as unsigned. The only snippet which
>> could be reviewed as controversy point  - is touch_nmi_watchdog()
>> where we just test nmi_watchdog for being greater than 0. Actually
>> there NMI_NONE should be used instead. But frankly some additional
>> simplification is needed.
>
> Don't forget that the NMI_DEFAULT symbol in include/asm-x86/nmi.h also
> equals to
> NMI_DISABLED, which is -1.
>
> 	Márton Németh
>
>
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