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

Andrew Morton
2012-03-09T00:07:37Z

On Thu, 8 Mar 2012 15:44:16 -0800
Diwakar Tundlam <dtundlam@nvidia.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@nvidia.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;