Fix: close profiler drain and mapping races

[zhusy54]

Problem

Runtime replenishment can append to dev_to_host_ and block_ranges_
while drain shards call resolve_host_ptr(). The writer held
mapping_mutex_, but the reader relied on an invalid immutability assumption,
so container rehash or reallocation could race with lookup.

The drain loop also loaded the requested quiesce epoch after scanning its
queues. A sweep that began before the request could therefore acknowledge the
new epoch and let export begin before records published during that sweep were
drained.

Follow-up to #2127.

Changes

• Protect exact and block-range resolution with a shared mapping lock while
  keeping runtime mutation under the exclusive lock.
• Observe the requested quiesce epoch before each full drain sweep and only
  acknowledge that epoch after the sweep reports no work.
• Add concurrent exact/range mapping coverage and a gated regression test for
  the stale-sweep acknowledgement ordering.
• Make the test publisher follow device entry-before-tail ordering, document
  the mapping ownership contract, and apply the repository's #pragma once
  convention to the touched headers.

Reviewer guide

The main correctness boundaries are the lifetime of the shared mapping lock in
resolve_host_ptr() and the placement of the acquire-load before the complete
queue sweep in mgmt_drain_loop().

Testing

• Full no-hardware C++ unit suite: 135/135 passed
• test_profiler_base: 10/10 passed
• New quiesce regression: old implementation failed; fixed implementation
  passed 20 consecutive runs
• Concurrent mapping test passed under ThreadSanitizer
• Concurrent mapping test passed 50 consecutive runs

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Team

Run ID: acd2a8ad-5668-425b-9bf3-9fabfc8ed04b

📥 Commits

Reviewing files that changed from the base of the PR and between 5d046b1 and 843af9e.

📒 Files selected for processing (4)

• src/common/platform/include/host/buffer_pool_manager.h
• src/common/platform/include/host/profiler_base.h
• tests/ut/cpp/common/test_buffer_pool_manager.cpp
• tests/ut/cpp/common/test_profiler_base.cpp

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The changes add reader-writer locking to host pointer mappings and align profiler quiescence acknowledgements with queue sweeps. Unit tests cover concurrent mapping resolution and explicit buffer publication ordering.

Changes

Host mapping synchronization

Layer / File(s)	Summary
Mapping locking and concurrent resolution src/common/platform/include/host/buffer_pool_manager.h, tests/ut/cpp/common/test_buffer_pool_manager.cpp	The buffer pool manager uses exclusive locks for mapping updates and shared locks for pointer lookups. A concurrent test resolves exact and inner-range pointers while another thread registers 2048 blocks.

Profiler drain epoch ordering

Layer / File(s)	Summary
Drain epoch ordering and queue publication src/common/platform/include/host/profiler_base.h, tests/ut/cpp/common/test_profiler_base.cpp	The drain worker samples the quiescence epoch before sweeping queues. Test helpers now register buffers separately and issue a write barrier before advancing queue tails.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 843af

This change synchronizes concurrent host-mapping access and makes profiler drain acknowledgements correspond to post-epoch sweeps, with updated coverage for concurrent resolution and publication ordering. No concrete current-head merge-blocking risk remains.

Poem

A rabbit guards the mapping gate
Shared locks let readers congregate
The drain marks time before its sweep
Queue tails wake from orderly sleep
Blocks resolve through thicket and stream
Safe little pointers hop in a dream

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 63.16% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and clearly summarizes the two main fixes: profiler drain races and mapping races.
Description check	✅ Passed	The description directly explains the mapping and profiler drain races, the implemented fixes, test coverage, and reviewer focus.

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