linux-kernel - [PATCH v2 TSC and clocksource-watchdog updates for v6.12 3/5] clocksource: Fix comments on WATCHDOG_THRESHOLD & WATCHDOG_MAX

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Message-Id: <20240802154618.4149953-3-paulmck@kernel.org>
Date: Fri,  2 Aug 2024 08:46:16 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>,
	John Stultz <jstultz@...gle.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Feng Tang <feng.tang@...el.com>,
	Waiman Long <longman@...hat.com>,
	Neeraj Upadhyay <Neeraj.Upadhyay@....com>,
	x86@...nel.org,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH v2 TSC and clocksource-watchdog updates for v6.12 3/5]  clocksource: Fix comments on WATCHDOG_THRESHOLD & WATCHDOG_MAX_SKEW

The WATCHDOG_THRESHOLD macro is no longer used to supply a default value
for ->uncertainty_margin, but WATCHDOG_MAX_SKEW now is.  Therefore,
update the comments to reflect this change.

Reported-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 kernel/time/clocksource.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 581cdbb538448..ee0ad5e4d5170 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -113,7 +113,6 @@ static u64 suspend_start;
 
 /*
  * Threshold: 0.0312s, when doubled: 0.0625s.
- * Also a default for cs->uncertainty_margin when registering clocks.
  */
 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
 
@@ -139,6 +138,13 @@ static u64 suspend_start;
 #define MAX_SKEW_USEC	(125 * WATCHDOG_INTERVAL / HZ)
 #endif
 
+/*
+ * Default for maximum permissible skew when cs->uncertainty_margin is
+ * not specified, and the lower bound even when cs->uncertainty_margin
+ * is specified.  This is also the default that is used when registering
+ * clocks with unspecifed cs->uncertainty_margin, so this macro is used
+ * even in CONFIG_CLOCKSOURCE_WATCHDOG=n kernels.
+ */
 #define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
-- 
2.40.1