From: Thomas Gleixner Date: Fri, 23 Jan 2026 23:17:57 +0000 (+0100) Subject: clocksource: Don't use non-continuous clocksources as watchdog X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1432f9d4e8aa2d7585b678bdd0b740597af00d6e;p=thirdparty%2Fkernel%2Flinux.git clocksource: Don't use non-continuous clocksources as watchdog Using a non-continuous aka untrusted clocksource as a watchdog for another untrusted clocksource is equivalent to putting the fox in charge of the henhouse. That's especially true with the jiffies clocksource which depends on interrupt delivery based on a periodic timer. Neither the frequency of that timer is trustworthy nor the kernel's ability to react on it in a timely manner and rearm it if it is not self rearming. Just don't bother to deal with this. It's not worth the trouble and only relevant to museum piece hardware. Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260123231521.858743259@kernel.org --- diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 3c205447717ae..e753a0632ac80 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -651,6 +651,13 @@ static void clocksource_select_watchdog(bool fallback) if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) continue; + /* + * If it's not continuous, don't put the fox in charge of + * the henhouse. + */ + if (!(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)) + continue; + /* Skip current if we were requested for a fallback. */ if (fallback && cs == old_wd) continue;