linux-kernel - Re: [PATCH 02/22] m68k/mac: macints - Modernize printing of kernel messages

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Date:   Fri, 9 Dec 2016 10:11:36 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
cc:     Greg Ungerer <gerg@...ux-m68k.org>, Sam Creasey <sammy@...my.net>,
        Joshua Thompson <funaho@...ai.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/22] m68k/mac: macints - Modernize printing of kernel
 messages


On Thu, 8 Dec 2016, Geert Uytterhoeven wrote:

> On Wed, Dec 7, 2016 at 11:45 PM, Finn Thain <fthain@...egraphics.com.au> wrote:
> > On Wed, 7 Dec 2016, Geert Uytterhoeven wrote:
> >
> >>   - Introduce helpers for printing debug messages, incl. dummies for
> >>     validating format strings when debugging is disabled,
> >>   - Convert from printk() to pr_*(),
> >>   - Add missing continuations, to fix user-visible breakage.
> >>
> >> Fixes: 4bcc595ccd80decb ("printk: reinstate KERN_CONT for printing continuation lines")
> >> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> >> ---
> >>  arch/m68k/mac/macints.c | 42 ++++++++++++++++++++++--------------------
> >>  1 file changed, 22 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/arch/m68k/mac/macints.c b/arch/m68k/mac/macints.c
> >> index 9f98c08719010e27..8572290cb93b6679 100644
> >> --- a/arch/m68k/mac/macints.c
> >> +++ b/arch/m68k/mac/macints.c
> >> @@ -135,6 +135,11 @@
> >>  irqreturn_t mac_debug_handler(int, void *);
> >>
> >>  /* #define DEBUG_MACINTS */
> >> +#ifdef DEBUG_MACINTS
> >> +#define pr_irq(fmt, ...) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> >> +#else
> >> +#define pr_irq(fmt, ...) no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> >> +#endif
> >>
> >>  static unsigned int mac_irq_startup(struct irq_data *);
> >>  static void mac_irq_shutdown(struct irq_data *);
> >
> > I would prefer to delete all the DEBUG_MACINTS clutter.
> 
> OK, can do that.

Thanks.

> 
> >> @@ -281,7 +282,7 @@ static void mac_irq_shutdown(struct irq_data *data)
> >>  irqreturn_t mac_debug_handler(int irq, void *dev_id)
> >>  {
> >>       if (num_debug[irq] < 10) {
> >> -             printk("DEBUG: Unexpected IRQ %d\n", irq);
> >> +             pr_info("DEBUG: Unexpected IRQ %d\n", irq);
> >>               num_debug[irq]++;
> >>       }
> >>       return IRQ_HANDLED;
> >
> > Is this dead code?
> 
> Yes, mac_debug_handler() is unused.
> 
> Removing that can be done in a separate patch (this is one of the 
> patches I'd like to send upstream ASAP).

OK.

> 
> >> @@ -319,20 +320,21 @@ irqreturn_t mac_nmi_handler(int irq, void *dev_id)
> >>  #if 0
> >>               struct pt_regs *fp = get_irq_regs();
> >>               show_state();
> >> -             printk("PC: %08lx\nSR: %04x  SP: %p\n", fp->pc, fp->sr, fp);
> >> -             printk("d0: %08lx    d1: %08lx    d2: %08lx    d3: %08lx\n",
> >> -                    fp->d0, fp->d1, fp->d2, fp->d3);
> >> -             printk("d4: %08lx    d5: %08lx    a0: %08lx    a1: %08lx\n",
> >> -                    fp->d4, fp->d5, fp->a0, fp->a1);
> >> +             pr_info("PC: %08lx\nSR: %04x  SP: %p\n", fp->pc, fp->sr, fp);
> >> +             pr_info("d0: %08lx    d1: %08lx    d2: %08lx    d3: %08lx\n",
> >> +                     fp->d0, fp->d1, fp->d2, fp->d3);
> >> +             pr_info("d4: %08lx    d5: %08lx    a0: %08lx    a1: %08lx\n",
> >> +                     fp->d4, fp->d5, fp->a0, fp->a1);
> >>
> >>               if (STACK_MAGIC != *(unsigned long *)current->kernel_stack_page)
> >> -                     printk("Corrupted stack page\n");
> >> -             printk("Process %s (pid: %d, stackpage=%08lx)\n",
> >> -                     current->comm, current->pid, current->kernel_stack_page);
> >> +                     pr_info("Corrupted stack page\n");
> >> +             pr_info("Process %s (pid: %d, stackpage=%08lx)\n",
> >> +                     current->comm, current->pid,
> >> +                     current->kernel_stack_page);
> >>               if (intr_count == 1)
> >>                       dump_stack((struct frame *)fp);
> >>  #else
> >> -             /* printk("NMI "); */
> >> +             /* pr_info("NMI "); */
> >>  #endif
> >>       }
> >>       in_nmi--;
> >>
> >
> > I think it would be good to use pr_debug here instead of #if 0. But that
> > will probably break the build... better ignore the #if 0 section for this
> > series, until I put together a different patch?
> 
> Or worse, break at runtime.
> 

The NMI isn't easily tiggered, unless you know how. It's solely for 
developers.

Anyway, this is dead code so it makes little difference whether you patch 
it or not. But this hunk will break an NMI debug patch that I've been 
using for ten years or so. Since this code needs a rewrite anyway, you 
might as well avoid the churn IMHO.

> There's also non-printing code in that block.

But no side-effects, right?

-- 

> Gr{oetje,eeting}s,
> 
>                         Geert
>