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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
| commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
| tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /Documentation/trace/rv/monitor_wip.rst | |
| parent | Initial commit. (diff) | |
| download | linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip | |
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/trace/rv/monitor_wip.rst')
| -rw-r--r-- | Documentation/trace/rv/monitor_wip.rst | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/Documentation/trace/rv/monitor_wip.rst b/Documentation/trace/rv/monitor_wip.rst new file mode 100644 index 000000000..a95763438 --- /dev/null +++ b/Documentation/trace/rv/monitor_wip.rst @@ -0,0 +1,55 @@ +Monitor wip +=========== + +- Name: wip - wakeup in preemptive +- Type: per-cpu deterministic automaton +- Author: Daniel Bristot de Oliveira <bristot@kernel.org> + +Description +----------- + +The wakeup in preemptive (wip) monitor is a sample per-cpu monitor +that verifies if the wakeup events always take place with +preemption disabled:: + + | + | + v + #==================# + H preemptive H <+ + #==================# | + | | + | preempt_disable | preempt_enable + v | + sched_waking +------------------+ | + +--------------- | | | + | | non_preemptive | | + +--------------> | | -+ + +------------------+ + +The wakeup event always takes place with preemption disabled because +of the scheduler synchronization. However, because the preempt_count +and its trace event are not atomic with regard to interrupts, some +inconsistencies might happen. For example:: + + preempt_disable() { + __preempt_count_add(1) + -------> smp_apic_timer_interrupt() { + preempt_disable() + do not trace (preempt count >= 1) + + wake up a thread + + preempt_enable() + do not trace (preempt count >= 1) + } + <------ + trace_preempt_disable(); + } + +This problem was reported and discussed here: + https://lore.kernel.org/r/cover.1559051152.git.bristot@redhat.com/ + +Specification +------------- +Grapviz Dot file in tools/verification/models/wip.dot |