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| author | Chao Liu <chao.liu@processmission.com> | 2026-07-29 16:11:02 +0800 |
|---|---|---|
| committer | Gabriele Monaco <gmonaco@redhat.com> | 2026-08-04 16:11:28 +0200 |
| commit | 7d81675d1bb2cc6db61a2d93b1e0dc7fb0929f9c (patch) | |
| tree | c7eaa0bc3ab935cae3bff8b8c6f5644f4771da2e | |
| parent | 785095112f4198de49760552374f364043c8dbdf (diff) | |
Documentation/rv: Explain epoll and aborted sleeps
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.
Signed-off-by: Chao Liu <chao.liu@processmission.com>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20260729081102.73138-1-chao.liu@processmission.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
| -rw-r--r-- | Documentation/trace/rv/monitor_rtapp.rst | 6 |
1 files changed, 6 insertions, 0 deletions
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: |