[PATCH v2] watchdog: Improve initialisation error message and documentation

[Ben Hutchings <ben@decadent.org.uk>]

The error message 'NMI watchdog failed to create perf event...'  does
not make it clear that this is a fatal error for the watchdog.  It
also currently prints the error value as a pointer, rather than
extracting the error code with PTR_ERR().  Fix that.

Add a note to the description of the 'nowatchdog' kernel parameter to
associate it with this message.

Reported-by: Cesare Leonardi <celeonar@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
Further improved the error message based on Cesare's comments.

Ben.

 Documentation/kernel-parameters.txt |    2 +-
 kernel/watchdog.c                   |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7d0cead..6fc0cf4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1764,7 +1764,7 @@ and is between 256 and 4096 characters. It is defined in the file
 
 	nousb		[USB] Disable the USB subsystem
 
-	nowatchdog	[KNL] Disable the lockup detector.
+	nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
 
 	nowb		[ARM]
 
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d74e866..d7ebdf4 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -366,7 +366,8 @@ static int watchdog_nmi_enable(int cpu)
 		goto out_save;
 	}
 
-	printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
+	printk(KERN_ERR "NMI watchdog disabled for cpu%i: unable to create perf event: %ld\n",
+	       cpu, PTR_ERR(event));
 	return PTR_ERR(event);
 
 	/* success path */
-- 
1.7.2.3