linux-kernel - Re: [PATCH 1/2] watchdog: Fix output

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Message-ID: <20160318163748.GR64531@redhat.com>
Date:	Fri, 18 Mar 2016 12:37:48 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	mingo@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH 1/2] watchdog: Fix output

On Fri, Mar 18, 2016 at 04:28:03PM +0100, Peter Zijlstra wrote:
> The pr_crap() functions generate idiotic output; use printk().
> 
> Broken output:
> 
> [ 3538.718135] NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s!  [perf_fuzzer:2646]
> [ 3383.233583] NMI watchdog: Watchdog detected hard LOCKUP on cpu 27
> 
> Fixed output:
> 
> [14180.328194] BUG: soft lockup - CPU#2 stuck for 23s!  [perf_fuzzer:13650]
> [ 1064.914925] BUG: NMI Watchdog detected hard LOCKUP on cpu 11

Would something like this be a better patch?

Cheers,
Don



diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index b3ace6e..e3302a0 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -9,7 +9,7 @@
  * to those contributors as well.
  */
 
-#define pr_fmt(fmt) "NMI watchdog: " fmt
+#define pr_fmt(fmt) "Lockup detector: " fmt
 
 #include <linux/mm.h>
 #include <linux/cpu.h>
@@ -350,7 +350,7 @@ static void watchdog_overflow_callback(struct perf_event *event,
 		if (__this_cpu_read(hard_watchdog_warn) == true)
 			return;
 
-		pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
+		pr_emerg("Detected hard LOCKUP on cpu %d", this_cpu);
 		print_modules();
 		print_irqtrace_events(current);
 		if (regs)
@@ -467,7 +467,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 			}
 		}
 
-		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
+		pr_emerg("Detected soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 			smp_processor_id(), duration,
 			current->comm, task_pid_nr(current));
 		__this_cpu_write(softlockup_task_ptr_saved, current);
> 
> Cc: Don Zickus <dzickus@...hat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/watchdog.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -350,7 +350,7 @@ static void watchdog_overflow_callback(s
>  		if (__this_cpu_read(hard_watchdog_warn) == true)
>  			return;
>  
> -		pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> +		printk(KERN_EMERG "BUG: NMI detected hard LOCKUP on cpu %d", this_cpu);
>  		print_modules();
>  		print_irqtrace_events(current);
>  		if (regs)
> @@ -467,7 +467,7 @@ static enum hrtimer_restart watchdog_tim
>  			}
>  		}
>  
> -		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
> +		printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
>  			smp_processor_id(), duration,
>  			current->comm, task_pid_nr(current));
>  		__this_cpu_write(softlockup_task_ptr_saved, current);
> 
>