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<a href="https://gitlab.rtems.org/karthikey_kadati">Karthikey Kadati</a> created a merge request: <a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/882">!882</a>
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Project:Branches: karthikey_kadati/rtems:feature-fmlp-port to rtems/rtos/rtems:main
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Author: Karthikey Kadati
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Assignees:
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Reviewers:
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">This MR introduces the Flexible Multiprocessor Locking Protocol (FMLP) into the RTEMS 7 SMP SuperCore. It implements both the FMLP-Short (busy-wait) and FMLP-Long (suspension) variants. This addresses a significant gap in predictable multiprocessor resource sharing as documented in the TU Dortmund research.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">Technical Details</strong> The implementation modernizes the research patch by Junjie Shi et al. (2020) to align with current RTEMS 7 architecture.</p>
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<strong style="font-weight: 600; margin-top: 0;">SuperCore Logic</strong>: Logic for <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>FMLPS_Control</code> (Short) and <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>FMLPL_Control</code> (Long) has been added to <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>cpukit/score</code>.</li>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">Locking Mechanisms:</strong></p>
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<strong style="font-weight: 600; margin-top: 0;">FMLP-Short</strong>: Implements priority ceiling enforcement for non-preemptive busy-waiting.</li>
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<strong style="font-weight: 600; margin-top: 0;">FMLP-Long</strong>: Implements priority inheritance and boosting mechanisms for suspension-based locking.</li>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">Wait Discipline:</strong> Both variants utilize a FIFO wait-queue discipline, departing from standard priority-sorted queues to ensure predictable multiprocessor behavior.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">SMP Safety:</strong> All operations are updated to use the modern <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; font-weight: inherit; white-space: break-spaces; overflow-wrap: break-word; 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;'>Thread_queue_Context</code> to ensure atomic state transitions.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">API and Observability</strong></p>
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<strong style="font-weight: 600; margin-top: 0;">Classic API</strong>: Extended the Semaphore Manager attributes to include <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>RTEMS_FLEXIBLE_MULTIPROCESSOR_LOCKING_SHORT</code> and <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>RTEMS_FLEXIBLE_MULTIPROCESSOR_LOCKING_LONG</code>.</li>
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<strong style="font-weight: 600; margin-top: 0;">Monitor</strong>: Updated <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; 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; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>cpukit/libmisc/monitor/mon-sema.c</code> to identify and display these new semaphore types correctly.</li>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><strong style="font-weight: 600; margin-top: 0;">Verification</strong> Testing was performed on the SIS Simulator (SPARC/LEON3) with a 2-CPU SMP configuration.</p>
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<strong style="font-weight: 600; margin-top: 0;">spfmlp01</strong>: Validates FMLP-Long (suspension, priority inheritance, deadlock-free release).</li>
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<strong style="font-weight: 600; margin-top: 0;">spfmlp02</strong>: Validates FMLP-Short (busy-wait, priority ceiling enforcement).</li>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">Updates <a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/issues/4612" data-reference-type="issue" data-original="#4612" data-link="false" data-link-reference="false" data-issue="27176" data-project="26" data-iid="4612" data-namespace-path="rtems/rtos/rtems" data-project-path="rtems/rtos/rtems" data-issue-type="issue" data-container="body" data-placement="top" title="Locking Protocols for Multiprocessors" class="gfm gfm-issue" style="margin-top: 0;">#4612</a></p>
<p dir="auto" style="color: #3a383f; margin: 0;" align="initial">Signed-off-by: Karthikey D Kadati <a href="mailto:karthikey3608@gmail.com" style="margin-top: 0;">karthikey3608@gmail.com</a></p>
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