linux-kernel - [PATCH v2] watchdog: Reduce message verbosity

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Message-Id: <20180803060943.2643-1-okaya@kernel.org>
Date:   Thu,  2 Aug 2018 23:09:41 -0700
From:   Sinan Kaya <okaya@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Sinan Kaya <okaya@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Don Zickus <dzickus@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v2] watchdog: Reduce message verbosity

Code is emitting the following error message during boot on systems
without PMU hardware support while probing NMI capability.

NMI watchdog: Perf event create on CPU 0 failed with -2

This error is coming from this path:

lockup_detector_init
  watchdog_nmi_probe
    hardlockup_detector_perf_init
      hardlockup_detector_event_create
        perf_event_create_kernel_counter
          perf_event_alloc
            perf_init_event (9539)
              pmu = ERR_PTR(-ENOENT) due to lack of PMUs in the system

followed by the warning that NMI watchdog is disabled as follows.

NMI watchdog: Perf NMI watchdog permanently disabled

While NMI disabled information is usefel for ordinary users, seeing
a PERF event create failed with error code -2 is too verbose.

Reducing the message severity to debug so that if somebody is really
wants to debug this, they can find out the error source by increasing
the kernel loglevel during boot.

Signed-off-by: Sinan Kaya <okaya@...nel.org>
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=599368
---
 kernel/watchdog_hld.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index e449a23e9d59..1f7020d65d0a 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -175,8 +175,8 @@ static int hardlockup_detector_event_create(void)
 	evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
 					       watchdog_overflow_callback, NULL);
 	if (IS_ERR(evt)) {
-		pr_info("Perf event create on CPU %d failed with %ld\n", cpu,
-			PTR_ERR(evt));
+		pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
+			 PTR_ERR(evt));
 		return PTR_ERR(evt);
 	}
 	this_cpu_write(watchdog_ev, evt);
-- 
2.17.1