CP-49141: Mark the DB lock as high priority: try to avoid voluntary T…

…hread.yield while we hold it

We'd still yield when the tick thread yields, or on syscalls.

ocaml/database/db_lock.ml

@@ -79,9 +79,11 @@ module ReentrantLock : REENTRANT_LOCK = struct
 
   let current_tid () = Thread.(self () |> id)
 
-  let[@inline never] [@specialize never] lock_acquired () = ()
+  let[@inline never] [@specialize never] lock_acquired () =
+    Xapi_timeslice.Timeslice.lock_acquired ()
 
-  let[@inline never] [@specialize never] lock_released () = ()
+  let[@inline never] [@specialize never] lock_released () =
+    Xapi_timeslice.Timeslice.lock_released ()
 
   let lock l =
     let me = current_tid () in

ocaml/database/dune

@@ -48,6 +48,7 @@
     xapi-stdext-std
     xapi-stdext-threads
     xapi-stdext-unix
+    xapi_timeslice
     xml-light2
     xmlm
   )