On Wed, 2026-07-29 at 16:11 +0800, Chao Liu wrote: > epoll_wait() is a valid sleeping reason for real-time tasks because it > uses PI-aware locking, but the rtapp sleep monitor documentation only > discusses clock_nanosleep() and futexes. Document it. > > ABORT_SLEEP represents a task restoring TASK_RUNNING before entering > the scheduler. Since the task does not actually block, it becomes > runnable again without a wakeup sequence unsafe for real-time. Document > this behavior. >
Looks good, thanks! Please next time you send a patch, even if it's an RFC, put the extra comments after the --- . This way I can pull it directly without changing the commit message because git am ignores everything after the --- . Also, no big deal, but for simple patches like this one, and even after getting comments, there's no need to mark as RFC. Reviewed-by: Gabriele Monaco <[email protected]> I'd appreciate an ack from Nam, then I might be able to squeeze this before the merge window together with the last fixes. Thanks, Gabriele > This RFC is based on Nam Cao's pending "rv: rtapp monitor update" v2 > series: > > https://lore.kernel.org/r/[email protected] > > Signed-off-by: Chao Liu <[email protected]> > --- > Changes in v2: > - Explain why epoll_wait() is RT-safe in terms of PI-aware locking. > - Explain that ABORT_SLEEP does not require an RT-unsafe wakeup sequence. > - Update the commit message accordingly. > > Link to v1: > https://lore.kernel.org/linux-trace-kernel/[email protected]/ > > Documentation/trace/rv/monitor_rtapp.rst | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/trace/rv/monitor_rtapp.rst > b/Documentation/trace/rv/monitor_rtapp.rst > index 238b59395ff5..b95994ade14a 100644 > --- a/Documentation/trace/rv/monitor_rtapp.rst > +++ b/Documentation/trace/rv/monitor_rtapp.rst > @@ -67,6 +67,8 @@ thread to sleep for one of the following reasons: > variables as safe for real-time. As an alternative, the librtpi library > exists to provide a conditional variable implementation that is correct > for > real-time applications in Linux. > + - Real-time thread waiting for events using `epoll_wait`, which is a > + real-time-safe syscall for sleeping as it uses PI-aware locking. > > Beside the reason for sleeping, the eventual waker should also be > real-time-safe. Namely, one of: > @@ -114,6 +116,10 @@ The monitor's specification is:: > ALLOWLIST = BLOCK_ON_RT_MUTEX > or FUTEX_LOCK_PI > > +`ABORT_SLEEP` represents a task restoring its state to `TASK_RUNNING` before > +entering the scheduler. In this case, the task does not actually block, so > the > +task is back to runnable without any wakeup sequence unsafe for real-time. > + > Beside the scenarios described above, this specification also defines an > allow list > to handle some special cases: > > > base-commit: 248951ddc14de84de3910f9b13f51491a8cd91df > prerequisite-patch-id: d8b6c952a954662852e6b0684e0a3386eaab7f41 > prerequisite-patch-id: 940f7637aeabe4ba15a09c048c6f48138406f332 > prerequisite-patch-id: b99812692691f76d825778e01a2e771e058febd6 > prerequisite-patch-id: 512c300dce2cb74ac9cc007f9234aa507ef5c008
