Re: [PATCH] console: allow log level threshold adjustments from serial console

[Andrew Cooper <andrew.cooper3@citrix.com>]

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On 22/09/15 13:45, Jan Beulich wrote:
> ... so that one doesn't always need to reboot to see more / fewer
> messages.
>
> Note that upper thresholds are sticky, i.e. while they get adjusted
> upwards when the lower threshold would otherwise end up above the upper
> one, they don't get adjusted when reducing the lower one.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> TBD: Should we also add a (more flexible) sysctl?

That would be nicer than using `xl debug-keys +++++; xl dmesg`

>
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -168,7 +168,7 @@ static void __init parse_guest_loglvl(ch
>       _parse_loglvl(s, &xenlog_guest_lower_thresh, &xenlog_guest_upper_thresh);
>   }
>   
> -static char * __init loglvl_str(int lvl)
> +static char *loglvl_str(int lvl)
>   {
>       switch ( lvl )
>       {
> @@ -181,6 +181,66 @@ static char * __init loglvl_str(int lvl)
>       return "???";
>   }
>   
> +static int *__read_mostly upper_thresh_adj = &xenlog_upper_thresh;
> +static int *__read_mostly lower_thresh_adj = &xenlog_lower_thresh;
> +static const char *__read_mostly thresh_adj = "standard";
> +
> +static void do_toggle_guest(unsigned char key, struct cpu_user_regs *regs)
> +{
> +    if ( upper_thresh_adj == &xenlog_upper_thresh )
> +    {
> +        upper_thresh_adj = &xenlog_guest_upper_thresh;
> +        lower_thresh_adj = &xenlog_guest_lower_thresh;
> +        thresh_adj = "guest";
> +    }
> +    else
> +    {
> +        upper_thresh_adj = &xenlog_upper_thresh;
> +        lower_thresh_adj = &xenlog_lower_thresh;
> +        thresh_adj = "standard";
> +    }
> +    printk("'%c' pressed -> %s log level adjustments enabled\n",
> +           key, thresh_adj);
> +}
> +
> +static void do_adj_thresh(unsigned char key)
> +{
> +    if ( *upper_thresh_adj < *lower_thresh_adj )
> +        *upper_thresh_adj = *lower_thresh_adj;
> +    printk("'%c' pressed -> %s log level: %s (rate limited %s)\n",
> +           key, thresh_adj, loglvl_str(*lower_thresh_adj),
> +           loglvl_str(*upper_thresh_adj));

It might be useful for this printk() to indicate whether it was the 
standard or the guest log level which was adjusted.

> +}
> +
> +static void do_inc_thresh(unsigned char key, struct cpu_user_regs *regs)
> +{
> +    ++*lower_thresh_adj;
> +    do_adj_thresh(key);
> +}
> +
> +static void do_dec_thresh(unsigned char key, struct cpu_user_regs *regs)
> +{
> +    if ( *lower_thresh_adj )
> +        --*lower_thresh_adj;
> +    do_adj_thresh(key);
> +}
> +
> +static struct keyhandler inc_thresh_keyhandler = {
> +    .irq_callback = 1,
> +    .u.irq_fn = do_inc_thresh,
> +    .desc = "increase log level threshold"
> +};
> +static struct keyhandler dec_thresh_keyhandler = {
> +    .irq_callback = 1,
> +    .u.irq_fn = do_dec_thresh,
> +    .desc = "decrease log level threshold"
> +};
> +static struct keyhandler toggle_guest_keyhandler = {
> +    .irq_callback = 1,
> +    .u.irq_fn = do_toggle_guest,
> +    .desc = "toggle host/guest log level adjustment"
> +};
> +

I am guessing from the looks of these that I should augment my 
keyhandler cleanup to also be able to register irq handlers from outside 
of common/keyhandler.c

~Andrew

>   /*
>    * ********************************************************
>    * *************** ACCESS TO CONSOLE RING *****************
> @@ -834,6 +894,9 @@ void __init console_endboot(void)
>           xen_rx = !xen_rx;
>   
>       register_keyhandler('w', &dump_console_ring_keyhandler);
> +    register_keyhandler('+', &inc_thresh_keyhandler);
> +    register_keyhandler('-', &dec_thresh_keyhandler);
> +    register_keyhandler('G', &toggle_guest_keyhandler);
>   
>       /* Serial input is directed to DOM0 by default. */
>       switch_serial_input();
>
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel


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