diff options
| author | Adrian Hunter <adrian.hunter@intel.com> | 2024-03-25 07:40:20 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-04-08 15:03:08 +0200 |
| commit | e809a80aa0bcf802f99407c23fd6be6fd4eb250a (patch) | |
| tree | f3f3587ffbc614247424cc7b8daf2d438aac520d /kernel/time | |
| parent | timekeeping: Fold in timekeeping_delta_to_ns() (diff) | |
| download | linux-e809a80aa0bcf802f99407c23fd6be6fd4eb250a.tar.xz linux-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')
| -rw-r--r-- | kernel/time/timekeeping.c | 12 |
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; } |