[tip: timers/core] time/jiffies: Register jiffies clocksource before usage

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     f24df84cbe05e4471c04ac4b921fc0340bbc7752
Gitweb:        https://git.kernel.org/tip/f24df84cbe05e4471c04ac4b921fc0340bbc7752
Author:        Thomas Gleixner <tglx@xxxxxxxxxx>
AuthorDate:    Tue, 09 Jun 2026 17:14:45 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxx>
CommitterDate: Sat, 13 Jun 2026 15:22:40 +02:00

time/jiffies: Register jiffies clocksource before usage

Teddy reported that a XEN HVM has a long boot delay, which was bisected to
the recent enhancements to the negative motion detection. It turned out
that the jiffies clocksource is used in early boot before it is registered,
which leaves the max_delta_raw field at zero. That causes the read out to
be clamped to the max delta of 0, which means time is not making progress.

Cure it by ensuring that it is initialized before its first usage in
timekeeping_init().

Fixes: 76031d9536a0 ("clocksource: Make negative motion detection more robust")
Reported-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Tested-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/87y0gn3fve.ffs@fw13
Closes: https://lore.kernel.org/all/1780914594.8631fc262581453bbf619ec5b2062170.19ea6c8227b000701b@xxxxxxxxxx
---
 kernel/time/jiffies.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 1c954f3..d514288 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -60,15 +60,14 @@ EXPORT_SYMBOL(get_jiffies_64);
 
 EXPORT_SYMBOL(jiffies);
 
-static int __init init_jiffies_clocksource(void)
-{
-	return __clocksource_register(&clocksource_jiffies);
-}
-
-core_initcall(init_jiffies_clocksource);
+static bool cs_jiffies_registered __initdata;
 
 struct clocksource * __init __weak clocksource_default_clock(void)
 {
+	if (!cs_jiffies_registered) {
+		__clocksource_register(&clocksource_jiffies);
+		cs_jiffies_registered = true;
+	}
 	return &clocksource_jiffies;
 }