*** [err]: Sanitizer error: ==================
WARNING: ThreadSanitizer: data race (pid=77380)
  Write of size 4 at 0x55e70ee77980 by main thread (mutexes: write M0):
    #0 moduleNotifyKeyUnlink /home/runner/work/redis/redis/src/module.c:13193 (redis-server+0x33246d) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #1 dbSetValue /home/runner/work/redis/redis/src/db.c:623 (redis-server+0x158aa4) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #2 setKeyByLink /home/runner/work/redis/redis/src/db.c:777 (redis-server+0x159406) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #3 setGenericCommand /home/runner/work/redis/redis/src/t_string.c:181 (redis-server+0x1a1ce2) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #4 setCommand /home/runner/work/redis/redis/src/t_string.c:443 (redis-server+0x1a22d8) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #5 call /home/runner/work/redis/redis/src/server.c:4035 (redis-server+0xe719f) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #6 processCommand /home/runner/work/redis/redis/src/server.c:4808 (redis-server+0xea119) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #7 processCommandAndResetClient /home/runner/work/redis/redis/src/networking.c:3497 (redis-server+0x13e076) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #8 processInputBuffer /home/runner/work/redis/redis/src/networking.c:3789 (redis-server+0x13e076)
    #9 processPendingCommandAndInputBuffer /home/runner/work/redis/redis/src/networking.c:3541 (redis-server+0x13fadf) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #10 processClientsFromIOThread /home/runner/work/redis/redis/src/iothread.c:619 (redis-server+0xc1cfa) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #11 handleClientsFromIOThread /home/runner/work/redis/redis/src/iothread.c:680 (redis-server+0xc1e59) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #12 aeProcessEvents /home/runner/work/redis/redis/src/ae.c:435 (redis-server+0xa861d) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #13 aeProcessEvents /home/runner/work/redis/redis/src/ae.c:360 (redis-server+0xa861d)
    #14 aeMain /home/runner/work/redis/redis/src/ae.c:495 (redis-server+0xa861d)
    #15 main /home/runner/work/redis/redis/src/server.c:8327 (redis-server+0x8b4c4) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)

  Previous read of size 4 at 0x55e70ee77980 by thread T3:
    #0 hashTypeLength /home/runner/work/redis/redis/src/t_hash.c:2299 (redis-server+0x1eb6b5) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #1 getObjectLength /home/runner/work/redis/redis/src/object.c:1009 (redis-server+0x151d69) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #2 populateDeltaHistograms /home/runner/work/redis/redis/src/lazyfree.c:33 (redis-server+0x2fd505) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    #3 kvsLazyfreeFree /home/runner/work/redis/redis/src/lazyfree.c:63 (redis-server+0x2fd505)
    #4 bioProcessBackgroundJobs /home/runner/work/redis/redis/src/bio.c:340 (redis-server+0x2b07cb) (BuildId: 56f4df0f306eff979d7ac5c7c665610cf8c07edb)
    ```

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Single guarded read reorder in hash length counting; intended behavior is preserved for subtractExpiredFields=1 callers.
> 
> **Overview**
> Fixes a ThreadSanitizer **data race** on `server.allow_access_expired` when background I/O computes hash lengths for keysizes histograms.
> 
> **`hashTypeLength`** now reads `server.allow_access_expired` only when `subtractExpiredFields` is true. Callers such as **`populateDeltaHistograms()`** on a BIO thread use `subtractExpiredFields==0`, so they no longer touch that flag while the main thread updates it during normal command processing. The “don’t subtract expired fields when access is allowed” behavior is unchanged for paths that actually request subtraction.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit 042fdc6bbc74f7c33b3678ee4bd994f04a138cba. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->