Messages in this thread Patch in this message | | | Date | Mon, 08 Apr 2024 13:10:33 -0000 | From | "tip-bot2 for Adrian Hunter" <> | Subject | [tip: timers/core] timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety |
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The following commit has been merged into the timers/core branch of tip:
Commit-ID: e809a80aa0bcf802f99407c23fd6be6fd4eb250a Gitweb: https://git.kernel.org/tip/e809a80aa0bcf802f99407c23fd6be6fd4eb250a Author: Adrian Hunter <adrian.hunter@intel.com> AuthorDate: Mon, 25 Mar 2024 08:40:20 +02:00 Committer: Thomas Gleixner <tglx@linutronix.de> CommitterDate: Mon, 08 Apr 2024 15:03:08 +02:00
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
--- kernel/time/timekeeping.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 749387f..d174840 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; }
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