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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     tglx@linutronix.de
Cc:     linux-kernel@vger.kernel.org, john.stultz@linaro.org,
        sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com,
        maz@kernel.org, kernel-team@meta.com, neeraju@codeaurora.org,
        ak@linux.intel.com, feng.tang@intel.com, zhengjun.xing@intel.com,
        "Paul E. McKenney" <paulmck@kernel.org>,
        John Stultz <jstultz@google.com>
Subject: [PATCH clocksource 3/6] clocksource: Improve read-back-delay message
Date:   Wed,  4 Jan 2023 17:06:58 -0800
Message-Id: <20230105010701.1773895-3-paulmck@kernel.org>
In-Reply-To: <20230105010429.GA1773522@paulmck-ThinkPad-P17-Gen-1>
References: <20230105010429.GA1773522@paulmck-ThinkPad-P17-Gen-1>
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When cs_watchdog_read() is unable to get a qualifying clocksource read
within the limit set by max_cswd_read_retries, it prints a message
and marks the clocksource under test as unstable.  But that message is
unclear to anyone unfamiliar with the code:

clocksource: timekeeping watchdog on CPU13: wd-tsc-wd read-back delay 1000614ns, attempt 3, marking unstable

Therefore, add some context so that the message appears as follows:

clocksource: timekeeping watchdog on CPU13: wd-tsc-wd excessive read-back delay of 1000614ns vs. limit of 125000ns, wd-wd read-back delay only 27ns, attempt 3, marking tsc unstable

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Feng Tang <feng.tang@intel.com>
---
 kernel/time/clocksource.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index a3d19f6660ac7..b59914953809f 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -260,8 +260,8 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow,
 			goto skip_test;
 	}
 
-	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd read-back delay of %lldns, attempt %d, marking unstable\n",
-		smp_processor_id(), cs->name, wd_delay, nretries);
+	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd excessive read-back delay of %lldns vs. limit of %ldns, wd-wd read-back delay only %lldns, attempt %d, marking %s unstable\n",
+		smp_processor_id(), cs->name, wd_delay, WATCHDOG_MAX_SKEW, wd_seq_delay, nretries, cs->name);
 	return WD_READ_UNSTABLE;
 
 skip_test:
-- 
2.31.1.189.g2e36527f23