From: Thomas Gleixner Date: Wed, 4 Mar 2026 18:49:29 +0000 (+0100) Subject: clocksource: Update clocksource::freq_khz on registration X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=53007d526e17d29f0e5b81c07eb594a93bc4d29c;p=thirdparty%2Fkernel%2Flinux.git clocksource: Update clocksource::freq_khz on registration Borislav reported a division by zero in the timekeeping code and random hangs with the new coupled clocksource/clockevent functionality. It turned out that the TSC clocksource is not always updating the freq_khz field of the clocksource on registration. The coupled mode conversion calculation requires the frequency and as it's not initialized the resulting factor is zero or a random value. As a consequence this causes a division by zero or random boot hangs. Instead of chasing down all clocksources which fail to update that member, fill it in at registration time where the caller has to supply the frequency anyway. Except for special clocksources like jiffies which never can have coupled mode. To make this more robust put a check into the registration function to validate that the caller supplied a frequency if the coupled mode feature bit is set. If not, emit a warning and clear the feature bit. Fixes: cd38bdb8e696 ("timekeeping: Provide infrastructure for coupled clockevents") Reported-by: Borislav Petkov Reported-by: Nathan Chancellor Signed-off-by: Thomas Gleixner Tested-by: Borislav Petkov Tested-by: Nathan Chancellor Link: https://patch.msgid.link/87cy1jsa4m.ffs@tglx Closes: https://lore.kernel.org/20260303213027.GA2168957@ax162 --- diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index df71949616584..3c205447717ae 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -1169,6 +1169,9 @@ void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, NSEC_PER_SEC / scale, sec * scale); + + /* Update cs::freq_khz */ + cs->freq_khz = div_u64((u64)freq * scale, 1000); } /* @@ -1241,6 +1244,10 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX)) cs->id = CSID_GENERIC; + + if (WARN_ON_ONCE(!freq && cs->flags & CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT)) + cs->flags &= ~CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT; + if (cs->vdso_clock_mode < 0 || cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) { pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",