linux-kernel - Re: [PATCH] init: check printed flag to skip printing message

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Date:	Thu, 8 Mar 2012 16:07:31 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Diwakar Tundlam <dtundlam@...dia.com>
Cc:	"'Phil Carmody'" <ext-phil.2.carmody@...ia.com>,
	"'Russell King'" <rmk+kernel@....linux.org.uk>,
	"'Greg Kroah-Hartman'" <gregkh@...e.de>,
	"'Sameer Nanda'" <snanda@...omium.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'Linus Torvalds'" <torvalds@...ux-foundation.org>,
	Mike Travis <travis@....com>
Subject: Re: [PATCH] init: check printed flag to skip printing message

On Thu, 8 Mar 2012 15:44:16 -0800
Diwakar Tundlam <dtundlam@...dia.com> wrote:

> Otherwise the 'Calibration skipped' message gets printed everytime a CPU is
> hotplugged in, cluttering console for systems that frequently hotplug CPUs.
> 
> Signed-off-by: Diwakar Tundlam <dtundlam@...dia.com>
> ---
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/init/calibrate.c b/init/calibrate.c
> index 5f117ca..fda0a7b 100644
> --- a/init/calibrate.c
> +++ b/init/calibrate.c
> @@ -267,7 +267,8 @@ void __cpuinit calibrate_delay(void)
>  
> 	if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
> 		lpj = per_cpu(cpu_loops_per_jiffy, this_cpu);
> -		pr_info("Calibrating delay loop (skipped) "
> +		if (!printed)
> +			pr_info("Calibrating delay loop (skipped) "
>  			"already calibrated this CPU");
> 	} else if (preset_lpj) {
> 		lpj = preset_lpj;

oops, yes.



Looking at that code, I think Mike broke it in 2009 with feae3203d71
("timers, init: Limit the number of per cpu calibration bootup
messages"):


: diff --git a/init/calibrate.c b/init/calibrate.c
: index a379c90..6eb48e5 100644
: --- a/init/calibrate.c
: +++ b/init/calibrate.c
: @@ -123,23 +123,26 @@ void __cpuinit calibrate_delay(void)
:  {
:  	unsigned long ticks, loopbit;
:  	int lps_precision = LPS_PREC;
: +	static bool printed;
:  
:  	if (preset_lpj) {
:  		loops_per_jiffy = preset_lpj;
: -		printk(KERN_INFO
: -			"Calibrating delay loop (skipped) preset value.. ");
: -	} else if ((smp_processor_id() == 0) && lpj_fine) {
: +		if (!printed)
: +			pr_info("Calibrating delay loop (skipped) "
: +				"preset value.. ");
: +	} else if ((!printed) && lpj_fine) {
:  		loops_per_jiffy = lpj_fine;

What's going on here?  Why should the value of `printed' affect the
value of loops_per_jiffy?

(lpj_fine is set only in x86 tsc code, under late_time_init(), and
late_time_init() is called before calibrate_delay(), so we got that
part right).

:  		loops_per_jiffy = lpj_fine;
: -		printk(KERN_INFO
: -			"Calibrating delay loop (skipped), "
: +		pr_info("Calibrating delay loop (skipped), "
:  			"value calculated using timer frequency.. ");
:  	} else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) {
: -		printk(KERN_INFO
: -			"Calibrating delay using timer specific routine.. ");
: +		if (!printed)
: +			pr_info("Calibrating delay using timer "
: +				"specific routine.. ");
:  	} else {
:  		loops_per_jiffy = (1<<12);
:  
: -		printk(KERN_INFO "Calibrating delay loop... ");
: +		if (!printed)
: +			pr_info("Calibrating delay loop... ");
:  		while ((loops_per_jiffy <<= 1) != 0) {
:  			/* wait for "start of" clock tick */
:  			ticks = jiffies;
: @@ -170,7 +173,10 @@ void __cpuinit calibrate_delay(void)
:  				loops_per_jiffy &= ~loopbit;
:  		}
:  	}
: -	printk(KERN_CONT "%lu.%02lu BogoMIPS (lpj=%lu)\n",
: +	if (!printed)
: +		pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
:  			loops_per_jiffy/(500000/HZ),
:  			(loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
: +
: +	printed = true;
:  }
: diff --git a/kernel/cpu.c b/kernel/cpu.c
: index 6ba0f1e..7c4e271 100644
: --- a/kernel/cpu.c
: +++ b/kernel/cpu.c
: @@ -392,10 +392,9 @@ int disable_nonboot_cpus(void)
:  		if (cpu == first_cpu)
:  			continue;
:  		error = _cpu_down(cpu, 1);
: -		if (!error) {
: +		if (!error)
:  			cpumask_set_cpu(cpu, frozen_cpus);
: -			printk("CPU%d is down\n", cpu);
: -		} else {
: +		else {
:  			printk(KERN_ERR "Error taking CPU%d down: %d\n",
:  				cpu, error);
:  			break;

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