On Mon, Apr 15, 2024, at 19:07, Christophe Leroy wrote: > Le 15/04/2024 à 17:35, Arnd Bergmann a écrit : >> >> I haven't seen a good solution here. Ideally we'd just define >> the functions unconditionally and have IS_ENABLED() take care >> of letting the compiler drop them silently, but that doesn't >> build because of missing struct members. >> >> I won't object to either an 'extern' declaration or the >> 'BUILD_BUG_ON()' if you and others prefer that, both are better >> than BUG() here. I still think my suggestion would be a little >> simpler. > > The advantage of the BUILD_BUG() against the extern is that the error > gets detected at buildtime. With the extern it gets detected only at > link-time. > > But agree with you, the missing struct members defeats the advantages of > IS_ENABLED(). > > At the end, how many instances of struct timekeeper do we have in the > system ? With a quick look I see only two instances: tkcore.timekeeper > and shadow_timekeeper. If I'm correct, wouldn't it just be simpler to > have the three debug struct members defined at all time ? Sure, this version looks fine to me, and passes a simple build test without CONFIG_DEBUG_TIMEKEEPING. Arnd diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h index 84ff2844df2a..485677a98b0b 100644 --- a/include/linux/timekeeper_internal.h +++ b/include/linux/timekeeper_internal.h @@ -124,7 +124,6 @@ struct timekeeper { u32 ntp_err_mult; /* Flag used to avoid updating NTP twice with same second */ u32 skip_second_overflow; -#ifdef CONFIG_DEBUG_TIMEKEEPING long last_warning; /* * These simple flag variables are managed @@ -135,7 +134,6 @@ struct timekeeper { */ int underflow_seen; int overflow_seen; -#endif }; #ifdef CONFIG_GENERIC_TIME_VSYSCALL diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4e18db1819f8..17f7aed807e1 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -195,7 +195,6 @@ static inline u64 tk_clock_read(const struct tk_read_base *tkr) return clock->read(clock); } -#ifdef CONFIG_DEBUG_TIMEKEEPING #define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */ static void timekeeping_check_update(struct timekeeper *tk, u64 offset) @@ -276,15 +275,6 @@ static inline u64 timekeeping_debug_get_ns(const struct tk_read_base *tkr) /* timekeeping_cycles_to_ns() handles both under and overflow */ return timekeeping_cycles_to_ns(tkr, now); } -#else -static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset) -{ -} -static inline u64 timekeeping_debug_get_ns(const struct tk_read_base *tkr) -{ - BUG(); -} -#endif /** * tk_setup_internals - Set up internals to use clocksource clock. @@ -2173,7 +2163,8 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode) goto out; /* Do some additional sanity checking */ - timekeeping_check_update(tk, offset); + if (IS_ENABLED(CONFIG_DEBUG_TIMEKEEPING)) + timekeeping_check_update(tk, offset); /* * With NO_HZ we may have to accumulate many cycle_intervals