[PATCH 2/3] [RFC] Print a watchdog message at KERN_WARNING level

[Paul Bolle]

For messages like
    NMI watchdog disabled for cpu0: unable to create perf event: -95

KERN_WARNING seems to be more appropriate than KERN_ERR. (Main benefit
of the KERN_WARNING level is that Fedora's plymouth bootsplash should
now hide them.)

Signed-off-by: Paul Bolle <pebolle(a)tiscali.nl&gt;
---
Yes, the changed line is getting very long, but that is apparently not a
problem in this file.

 kernel/watchdog.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index f37f974..1c2ffe1 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -363,7 +363,7 @@ static int watchdog_nmi_enable(int cpu)
 		goto out_save;
 	}
 
-	printk(KERN_ERR "NMI watchdog disabled for cpu%i: unable to create perf event:
%ld\n",
+	printk(KERN_WARNING "NMI watchdog disabled for cpu%i: unable to create perf event:
%ld\n",
 	       cpu, PTR_ERR(event));
 	return PTR_ERR(event);
 
-- 
1.7.4

[Don Zickus]

On Thu, Feb 03, 2011 at 11:08:10PM +0100, Paul Bolle wrote:
>  For messages like
>      NMI watchdog disabled for cpu0: unable to create perf event: -95
>  
>  KERN_WARNING seems to be more appropriate than KERN_ERR. (Main benefit
>  of the KERN_WARNING level is that Fedora's plymouth bootsplash should
>  now hide them.)
>  
>  Signed-off-by: Paul Bolle <pebolle(a)tiscali.nl&gt; 
Hi Paul,

Thanks for the patch.  I actually maintain this file upstream.  I am
concerned about the error you are seeing, -95.  Is it possible you can
provide me a 'dmesg' log of your boot up.  I want to see what chipset the
perf subsystem thinks it found.

I may want to handle this error a little bit differently than the patch
you provided below.

Thanks,
Don

>  ---
>  Yes, the changed line is getting very long, but that is apparently not a
>  problem in this file.
>  
>   kernel/watchdog.c |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>  
>  diff --git a/kernel/watchdog.c b/kernel/watchdog.c
>  index f37f974..1c2ffe1 100644
>  --- a/kernel/watchdog.c
>  +++ b/kernel/watchdog.c
>  @@ -363,7 +363,7 @@ static int watchdog_nmi_enable(int cpu)
>   		goto out_save;
>   	}
>   
>  -	printk(KERN_ERR "NMI watchdog disabled for cpu%i: unable to create perf event:
> %ld\n",
>  +	printk(KERN_WARNING "NMI watchdog disabled for cpu%i: unable to create perf event:
> %ld\n",
>   	       cpu, PTR_ERR(event));
>   	return PTR_ERR(event);
>   
>  -- 
>  1.7.4
>  
>  _______________________________________________
>  kernel mailing list
>  kernel(a)lists.fedoraproject.org
>  https://admin.fedoraproject.org/mailman/listinfo/kernel

[Paul Bolle]

On Fri, 2011-02-04 at 10:27 -0500, Don Zickus wrote:
>  I am concerned about the error you are seeing, -95.  Is it possible
> you can
>  provide me a 'dmesg' log of your boot up.  I want to see what chipset the
>  perf subsystem thinks it found. 
Sure, no problem. Off-list or on-list?

And what messages in dmesg are you interested in? All or just some?

I suppose I should try a boot without the "quiet" kernel parameter. Is
there some debug parameter that would be helpful here too?


Paul

[Don Zickus]

On Fri, Feb 04, 2011 at 06:32:33PM +0100, Paul Bolle wrote:
>  On Fri, 2011-02-04 at 10:27 -0500, Don Zickus wrote:
>  > I am concerned about the error you are seeing, -95.  Is it possible you can
>  > provide me a 'dmesg' log of your boot up.  I want to see what chipset the
>  > perf subsystem thinks it found.
>  
>  Sure, no problem. Off-list or on-list? 
on-list is fine.

>  
>  And what messages in dmesg are you interested in? All or just some?
>  
>  I suppose I should try a boot without the "quiet" kernel parameter. Is
>  there some debug parameter that would be helpful here too? 
you can just run 'dmesg > /tmp/dmesg.out' after you login and then attach
that file to a reply to this thread.  I'll I am interested in is the few
lines above the NMI watchdog error that starts with "Performance Events:"
But you can post the whole thing for completeness.

Cheers,
Don

[Paul Bolle]

On Fri, 2011-02-04 at 13:38 -0500, Don Zickus wrote:
>  [All] I am interested in is the few
>  lines above the NMI watchdog error that starts with "Performance Events:"
[    0.016136] Performance Events: 
[    0.016139] no APIC, boot with the "lapic" boot parameter to force-enable it
[    0.016142] no hardware sampling interrupt available.
[    0.016146] p6 PMU driver.
[    0.016151] ... version:                0
[    0.016153] ... bit width:              32
[    0.016156] ... generic registers:      2
[    0.016158] ... value mask:             00000000ffffffff
[    0.016161] ... max period:             000000007fffffff
[    0.016163] ... fixed-purpose events:   0
[    0.016166] ... event mask:             0000000000000003
[    0.017455] NMI watchdog disabled for cpu0: unable to create perf event: -95

Feel free to ask me for what else might be needed here.


Paul

[Don Zickus]

On Fri, Feb 04, 2011 at 08:42:34PM +0100, Paul Bolle wrote:
>  On Fri, 2011-02-04 at 13:38 -0500, Don Zickus wrote:
>  > [All] I am interested in is the few
>  > lines above the NMI watchdog error that starts with "Performance Events:"
>  
>  [    0.016136] Performance Events: 
>  [    0.016139] no APIC, boot with the "lapic" boot parameter to force-enable
> it
>  [    0.016142] no hardware sampling interrupt available.
>  [    0.016146] p6 PMU driver.
>  [    0.016151] ... version:                0
>  [    0.016153] ... bit width:              32
>  [    0.016156] ... generic registers:      2
>  [    0.016158] ... value mask:             00000000ffffffff
>  [    0.016161] ... max period:             000000007fffffff
>  [    0.016163] ... fixed-purpose events:   0
>  [    0.016166] ... event mask:             0000000000000003
>  [    0.017455] NMI watchdog disabled for cpu0: unable to create perf event: -95
>  
>  Feel free to ask me for what else might be needed here. 
Thanks for the info.  This is what I thought, the system has no lapic.  I
think I am going to re-arrange some code to properly deal with this
scenario.  Not having a lapic should not be a KERN_ERR, the nmi watchdog
should just accept it, print out a quiet message and move on. :-)

Thanks for finding this and providing the info!

Cheers,
Don

[Paul Bolle]

On Fri, 2011-02-04 at 17:16 -0500, Don Zickus wrote:

>  Thanks for finding this and providing the info! 
You're welcome. Feel free to ask me to test the rearranged code and/or
to a add Reported-by tag to your patch.


Paul

[Don Zickus]

On Fri, Feb 04, 2011 at 11:32:18PM +0100, Paul Bolle wrote:
>  On Fri, 2011-02-04 at 17:16 -0500, Don Zickus wrote:
>  
>  > Thanks for finding this and providing the info!
>  
>  You're welcome. Feel free to ask me to test the rearranged code and/or
>  to a add Reported-by tag to your patch. 
Hi Paul,

Here is a patch I was looking to post upstream.  This should address your
concerns.  Let me know how it works out for you.

Cheers,
Don

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d7ebdf4..bb7887b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -366,8 +366,17 @@ static int watchdog_nmi_enable(int cpu)
 		goto out_save;
 	}
 
-	printk(KERN_ERR "NMI watchdog disabled for cpu%i: unable to create perf event:
%ld\n",
-	       cpu, PTR_ERR(event));
+
+	/* vary the KERN level based on the returned errno */
+	if (PTR_ERR(event) == -EOPNOTSUPP)
+		printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported"
+				 " (no LAPIC?)\n", cpu);
+	else if (PTR_ERR(event) == -ENOENT)
+		printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware"
+				    " events not enabled\n", cpu);
+	else
+		printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create"
+				" perf event: %ld\n", cpu, PTR_ERR(event));
 	return PTR_ERR(event);
 
 	/* success path */

[Paul Bolle]

On Tue, 2011-02-08 at 16:46 -0500, Don Zickus wrote:
>  Here is a patch I was looking to post upstream.  This should address
> your
>  concerns.  Let me know how it works out for you. 
0) Compiles cleanly.
1) Nothing shows up anymore at boot a with Fedora's default command
line.
2) dmesg -r | grep NMI
<6>[    0.019692] NMI watchdog disabled (cpu0): not supported (no LAPIC?)

For what testing one of three branches is worth:

Tested-by: Paul Bolle <pebolle(a)tiscali.nl&gt;

Thanks,


Paul

[Don Zickus]

On Wed, Feb 09, 2011 at 02:10:49PM +0100, Paul Bolle wrote:
>  On Tue, 2011-02-08 at 16:46 -0500, Don Zickus wrote:
>  > Here is a patch I was looking to post upstream.  This should address your
>  > concerns.  Let me know how it works out for you.
>  
>  0) Compiles cleanly.
>  1) Nothing shows up anymore at boot a with Fedora's default command
>  line.
>  2) dmesg -r | grep NMI
>  <6>[    0.019692] NMI watchdog disabled (cpu0): not supported (no LAPIC?)
>  
>  For what testing one of three branches is worth:
>  
>  Tested-by: Paul Bolle <pebolle(a)tiscali.nl&gt; 
Thanks!

Cheers,
Don