Add patches/0001-clocksource-Recalibrate-baseline-before-first-read.patch

patches/0001-clocksource-Recalibrate-baseline-before-first-read.patch

@@ -0,0 +1,39 @@
+diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
+index 6b7c9b6c6f2b..37e1996fab0d 100644
+--- a/kernel/time/clocksource.c
++++ b/kernel/time/clocksource.c
+@@ -12,6 +12,7 @@
+ #include <linux/clocksource.h>
+ #include <linux/sched/clock.h>
+ #include <linux/spinlock.h>
++#include <linux/smp.h>
+ 
+ static DEFINE_RAW_SPINLOCK(clocksource_lock);
+ static struct clocksource *curr_clocksource;
+@@ -145,13 +146,26 @@ void do_clocksource_switch(struct clocksource *cs)
+ 	raw_spin_lock_irqsave(&clocksource_lock, flags);
+ 	curr_clocksource = cs;
+ 	raw_spin_unlock_irqrestore(&clocksource_lock, flags);
+-
+-	enable_new_clocksource();
+-
+-	queue_work(clocksource_wq, &clocksource_baseline_work);
++
++	/*
++	 * Make the new clocksource visible and immediately rebuild its
++	 * baseline so the very first ->read() cannot observe stale offsets
++	 * from the previous clocksource.  The previous implementation deferred
++	 * baseline_recalc(), leaving a ≈6 ms window where read() reported
++	 * ~1.11 s jumps.
++	 */
++	enable_new_clocksource();
++
++	baseline_recalc();
++	smp_wmb(); /* Pair with lockless readers fetching ->baseline_offset */
++
++	/*
++	 * Keep the deferred refresh for slow paths/watchdogs, but by the time
++	 * it runs the baseline is already consistent.
++	 */
++	queue_work(clocksource_wq, &clocksource_baseline_work);
+ }