summaryrefslogtreecommitdiffstats
path: root/kernel/time/timekeeping.c
diff options
context:
space:
mode:
authorAdrian Hunter <adrian.hunter@intel.com>2024-03-25 08:40:20 +0200
committerThomas Gleixner <tglx@linutronix.de>2024-04-08 15:03:08 +0200
commite809a80aa0bcf802f99407c23fd6be6fd4eb250a (patch)
treef3f3587ffbc614247424cc7b8daf2d438aac520d /kernel/time/timekeeping.c
parent3094c6db1cba0bbca6ea19c777762c26fee747d7 (diff)
downloadlinux-stable-e809a80aa0bcf802f99407c23fd6be6fd4eb250a.tar.gz
linux-stable-e809a80aa0bcf802f99407c23fd6be6fd4eb250a.tar.bz2
linux-stable-e809a80aa0bcf802f99407c23fd6be6fd4eb250a.zip
timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety
Open code clocksource_delta() in timekeeping_cycles_to_ns() so that overflow safety can be added efficiently. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-17-adrian.hunter@intel.com
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r--kernel/time/timekeeping.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 749387f22f0f..d17484082e2c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -367,7 +367,17 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles)
{
/* Calculate the delta since the last update_wall_time() */
- u64 delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+ u64 mask = tkr->mask, delta = (cycles - tkr->cycle_last) & mask;
+
+ if (IS_ENABLED(CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE)) {
+ /*
+ * Handle clocksource inconsistency between CPUs to prevent
+ * time from going backwards by checking for the MSB of the
+ * mask being set in the delta.
+ */
+ if (unlikely(delta & ~(mask >> 1)))
+ return tkr->xtime_nsec >> tkr->shift;
+ }
return ((delta * tkr->mult) + tkr->xtime_nsec) >> tkr->shift;
}