https://nalar.dev/tags/timekeeping/ Recent content in Timekeeping on Nalar Hugo en-us Tue, 22 Sep 2026 00:00:00 +0000 https://nalar.dev/timerfd-cancel-on-set-reports-realtime-clock-discontinuities/ Tue, 22 Sep 2026 00:00:00 +0000 https://nalar.dev/timerfd-cancel-on-set-reports-realtime-clock-discontinuities/ <p>A <code>timerfd</code> armed against wall-clock time can cross a discontinuous clock adjustment before its deadline. With <code>TFD_TIMER_CANCEL_ON_SET</code>, Linux exposes that event through the descriptor: a subsequent <code>read()</code> fails with <code>ECANCELED</code> rather than presenting the clock jump as an ordinary timer expiration.</p> <p>The flag is deliberately narrow. It applies only when <code>timerfd_settime()</code> arms an absolute timer on <code>CLOCK_REALTIME</code> or <code>CLOCK_REALTIME_ALARM</code>, and it changes the handling of discontinuous changes to those clocks.</p>