After picking up a new checkpoint, the next access by any session finds its cached dhandle marked OUTDATED in __session_find_dhandle ([src/session/session_dhandle.c:139-143|src/session/session_dhandle.c]), discards it, and attempts to reopen. Reopening a not-yet-open dhandle requires an exclusive write lock (__wt_session_lock_dhandle). With a large number of concurrent reader sessions, they all race to acquire the same exclusive write locks. Each failed attempt spins through the yield loop at [src/session/session_dhandle.c:280-285|src/session/session_dhandle.c] and increments dhandle_lock_blocked.

Please refer to WT-17761 for more details.