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Issue created by <a href="https://gitlab.rtems.org/sebhub">Sebastian Huber</a>: <a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/work_items/5684">#5684</a>
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<p dir="auto" style="color: #3a383f; margin: 0px 0px 1rem;" align="initial"><code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0px; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">or1k_interrupt_disable()</code> clears <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">SR.IEE</code>, the interrupt exception enable of
the supervision register. The tick timer of the architecture has an exception
enable of its own, <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">SR.TEE</code>, and the function leaves it set. Every RTEMS
critical section on this port therefore runs with the clock tick enabled, and
the tick handler walks the watchdog chains which the code it interrupts is in
the middle of. On a uniprocessor build an ISR lock is an interrupt disable and
nothing else, so nothing detects the reentry. <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">_CPU_ISR_Set_level()</code> carries the
same asymmetry: it sets both bits to enable interrupts and clears one bit to
disable them.</p>
<p dir="auto" style="color: #3a383f; margin: 0px 0px 1rem;" align="initial">The clock driver of the BSP compounds it. The tick timer compares the low 28
bits of its counter with the time period field, and the driver takes the next
period from the previous one. A handler which runs late writes a period which
the counter already passed, and the timer then waits for the counter to run
through the whole field. At 20 MHz that is 13.4 s, and the tick after it is late
by the same amount, so the clock never recovers. A tick masked through a
critical section is what makes the handler late.</p>
<p dir="auto" style="color: #3a383f; margin: 0px 0px 1rem;" align="initial">The BSP has no driver for the programmable interrupt controller and no way to
raise an interrupt in software, so the interrupt manager cannot enable, disable
or raise a vector, every test which calls <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0px; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">CallWithinISR()</code> waits forever, and
the interrupt critical tests are excluded.</p>
<p dir="auto" style="color: #3a383f; margin: 0px;" align="initial">Found while running the full test suite on Qemu. This description was created
with Claude Code assistance.</p>
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