linux-kernel - [PATCH 5/6] timekeeping: Use proper timekeeper for debug code

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Date:   Fri, 18 Aug 2017 11:51:01 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     Stafford Horne <shorne@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        John Stultz <john.stultz@...aro.org>
Subject: [PATCH 5/6] timekeeping: Use proper timekeeper for debug code

From: Stafford Horne <shorne@...il.com>

When CONFIG_DEBUG_TIMEKEEPING is enabled the timekeeping_check_update()
function will update status like last_warning and underflow_seen on the
timekeeper.

If there are issues found this state is used to rate limit the warnings
that get printed.

This rate limiting doesn't really really work if stored in real_tk as
the shadow timekeeper is overwritten onto real_tk at the end of every
update_wall_time() call, resetting last_warning and other statuses.

Fix rate limiting by using the shadow_timekeeper for
timekeeping_check_update().

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Miroslav Lichvar <mlichvar@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Stephen Boyd <stephen.boyd@...aro.org>
Fixes: commit 57d05a93ada7 ("time: Rework debugging variables so they aren't global")
Signed-off-by: Stafford Horne <shorne@...il.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 kernel/time/timekeeping.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cedafa0..8f58669 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2066,7 +2066,7 @@ void update_wall_time(void)
 		goto out;
 
 	/* Do some additional sanity checking */
-	timekeeping_check_update(real_tk, offset);
+	timekeeping_check_update(tk, offset);
 
 	/*
 	 * With NO_HZ we may have to accumulate many cycle_intervals
-- 
2.7.4