linux-kernel - Re: [tip:x86/uv] x86/UV: Add uvtrace support

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Date:	Mon, 11 Nov 2013 19:53:40 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	hpa@...or.com, paulus@...ba.org, linux-kernel@...r.kernel.org,
	travis@....com, a.p.zijlstra@...llo.nl, jason.wessel@...driver.com,
	acme@...stprotocols.net, hedi@....com, sivanich@....com,
	tglx@...utronix.de
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/uv] x86/UV: Add uvtrace support


* tip-bot for Mike Travis <tipbot@...or.com> wrote:

> Commit-ID:  8eba18428ac926f436064ac281e76d36d51bd631
> Gitweb:     http://git.kernel.org/tip/8eba18428ac926f436064ac281e76d36d51bd631
> Author:     Mike Travis <travis@....com>
> AuthorDate: Mon, 23 Sep 2013 16:25:06 -0500
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Tue, 24 Sep 2013 09:02:04 +0200
> 
> x86/UV: Add uvtrace support
> 
> This patch adds support for the uvtrace module by providing a
> skeleton call to the registered trace function.  It also
> provides another separate 'NMI' tracer that is triggered by the
> system wide 'power nmi' command.
> 
> Signed-off-by: Mike Travis <travis@....com>
> Reviewed-by: Dimitri Sivanich <sivanich@....com>
> Reviewed-by: Hedi Berriche <hedi@....com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> Cc: Jason Wessel <jason.wessel@...driver.com>
> Link: http://lkml.kernel.org/r/20130923212501.185052551@asylum.americas.sgi.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/x86/include/asm/uv/uv.h  |  8 ++++++++
>  arch/x86/platform/uv/uv_nmi.c | 13 ++++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)

So I only noticed this too late:

> diff --git a/arch/x86/include/asm/uv/uv.h b/arch/x86/include/asm/uv/uv.h
> index 6b964a0..8b1283d 100644
> --- a/arch/x86/include/asm/uv/uv.h
> +++ b/arch/x86/include/asm/uv/uv.h
> @@ -14,6 +14,13 @@ extern void uv_cpu_init(void);
>  extern void uv_nmi_init(void);
>  extern void uv_register_nmi_notifier(void);
>  extern void uv_system_init(void);
> +extern void (*uv_trace_nmi_func)(unsigned int reason, struct pt_regs *regs);
> +extern void (*uv_trace_func)(const char *f, const int l, const char *fmt, ...);
> +#define uv_trace(fmt, ...)						\
> +do {									\
> +	if (unlikely(uv_trace_func))					\
> +		(uv_trace_func)(__func__, __LINE__, fmt, ##__VA_ARGS__);\
> +} while (0)
>  extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
>  						 struct mm_struct *mm,
>  						 unsigned long start,
> @@ -26,6 +33,7 @@ static inline enum uv_system_type get_uv_system_type(void) { return UV_NONE; }
>  static inline int is_uv_system(void)	{ return 0; }
>  static inline void uv_cpu_init(void)	{ }
>  static inline void uv_system_init(void)	{ }
> +static inline void uv_trace(void *fmt, ...)	{ }
>  static inline void uv_register_nmi_notifier(void) { }
>  static inline const struct cpumask *
>  uv_flush_tlb_others(const struct cpumask *cpumask, struct mm_struct *mm,
> diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
> index 2579fbd..c171ca5 100644
> --- a/arch/x86/platform/uv/uv_nmi.c
> +++ b/arch/x86/platform/uv/uv_nmi.c
> @@ -1,5 +1,5 @@
>  /*
> - * SGI NMI support routines
> + * SGI NMI/TRACE support routines
>   *
>   *  This program is free software; you can redistribute it and/or modify
>   *  it under the terms of the GNU General Public License as published by
> @@ -36,6 +36,13 @@
>  #include <asm/uv/uv_hub.h>
>  #include <asm/uv/uv_mmrs.h>
>  
> +void (*uv_trace_func)(const char *f, const int l, const char *fmt, ...);
> +EXPORT_SYMBOL(uv_trace_func);
> +
> +void (*uv_trace_nmi_func)(unsigned int reason, struct pt_regs *regs);
> +EXPORT_SYMBOL(uv_trace_nmi_func);
> +
> +
>  /*
>   * UV handler for NMI
>   *
> @@ -551,6 +558,10 @@ int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
>  		return NMI_DONE;
>  	}
>  
> +	/* Call possible NMI trace function */
> +	if (unlikely(uv_trace_nmi_func))
> +		(uv_trace_nmi_func)(reason, regs);

Nothing actually uses the uv_trace() methods, plus nobody actually sets 
uv_trace_func.

Whatever hack this is, it has no place in the upstream kernel. I'll queue 
up a revert to make this pushable in this merge window.

Thanks,

	Ingo
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