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| author | Gabriele Monaco <gmonaco@redhat.com> | 2025-07-28 15:50:21 +0200 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-07-28 16:47:35 -0400 |
| commit | 614384533dfe99293a7ff1bce3d4389adadbb759 (patch) | |
| tree | 6d1e0b9410701820e57d19031e65b6d073bcc72e /Documentation/trace | |
| parent | e8440a88e56bb3aa24c384eec6de8bef1184bed2 (diff) | |
| download | linux-614384533dfe99293a7ff1bce3d4389adadbb759.tar.gz linux-614384533dfe99293a7ff1bce3d4389adadbb759.tar.bz2 linux-614384533dfe99293a7ff1bce3d4389adadbb759.zip | |
rv: Add opid per-cpu monitor
Add a per-cpu monitor as part of the sched model:
* opid: operations with preemption and irq disabled
Monitor to ensure wakeup and need_resched occur with irq and
preemption disabled or in irq handlers.
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/20250728135022.255578-10-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Acked-by: Nam Cao <namcao@linutronix.de>
Tested-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/rv/monitor_sched.rst | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/Documentation/trace/rv/monitor_sched.rst b/Documentation/trace/rv/monitor_sched.rst index 11ef963cb578..3f8381ad9ec7 100644 --- a/Documentation/trace/rv/monitor_sched.rst +++ b/Documentation/trace/rv/monitor_sched.rst @@ -341,6 +341,61 @@ can be triggered also by preemption, but cannot occur after the task got to | | switch_yield +-----------+ wakeup +Monitor opid +------------ + +The operations with preemption and irq disabled (opid) monitor ensures +operations like ``wakeup`` and ``need_resched`` occur with interrupts and +preemption disabled or during interrupt context, in such case preemption may +not be disabled explicitly. +``need_resched`` can be set by some RCU internals functions, in which case it +doesn't match a task wakeup and might occur with only interrupts disabled:: + + | sched_need_resched + | sched_waking + | irq_entry + | +--------------------+ + v v | + +------------------------------------------------------+ + +----------- | disabled | <+ + | +------------------------------------------------------+ | + | | ^ | + | | preempt_disable sched_need_resched | + | preempt_enable | +--------------------+ | + | v | v | | + | +------------------------------------------------------+ | + | | irq_disabled | | + | +------------------------------------------------------+ | + | | | ^ | + | irq_entry irq_entry | | | + | sched_need_resched v | irq_disable | + | sched_waking +--------------+ | | | + | +----- | | irq_enable | | + | | | in_irq | | | | + | +----> | | | | | + | +--------------+ | | irq_disable + | | | | | + | irq_enable | irq_enable | | | + | v v | | + | #======================================================# | + | H enabled H | + | #======================================================# | + | | ^ ^ preempt_enable | | + | preempt_disable preempt_enable +--------------------+ | + | v | | + | +------------------+ | | + +----------> | preempt_disabled | -+ | + +------------------+ | + | | + +-------------------------------------------------------+ + +This monitor is designed to work on ``PREEMPT_RT`` kernels, the special case of +events occurring in interrupt context is a shortcut to identify valid scenarios +where the preemption tracepoints might not be visible, during interrupts +preemption is always disabled. On non- ``PREEMPT_RT`` kernels, the interrupts +might invoke a softirq to set ``need_resched`` and wake up a task. This is +another special case that is currently not supported by the monitor. + References ---------- |