diff --git a/src/core/fifo_pool.ml b/src/core/fifo_pool.ml
index 38a07d3d..3e70e06b 100644
--- a/src/core/fifo_pool.ml
+++ b/src/core/fifo_pool.ml
@@ -28,7 +28,6 @@ type worker_state = {
 
 let[@inline] size_ (self : state) = Array.length self.threads
 let[@inline] num_tasks_ (self : state) : int = Bb_queue.size self.q
-let k_worker_state : worker_state TLS.t = TLS.create ()
 
 (*
 get_thread_state = TLS.get_opt k_worker_state
@@ -71,12 +70,6 @@ let schedule_w (self : worker_state) (task : task_full) : unit =
 let get_next_task (self : worker_state) =
   try Bb_queue.pop self.st.q with Bb_queue.Closed -> raise WL.No_more_tasks
 
-let get_thread_state () =
-  match TLS.get_exn k_worker_state with
-  | st -> st
-  | exception TLS.Not_set ->
-    failwith "Moonpool: get_thread_state called from outside a runner."
-
 let before_start (self : worker_state) =
   let t_id = Thread.id @@ Thread.self () in
   self.st.on_init_thread ~dom_id:self.dom_idx ~t_id ();
@@ -103,7 +96,6 @@ let worker_ops : worker_state WL.ops =
     WL.schedule = schedule_w;
     runner;
     get_next_task;
-    get_thread_state;
     around_task;
     on_exn;
     before_start;
diff --git a/src/core/worker_loop_.ml b/src/core/worker_loop_.ml
index bd2cd5ca..c375e8a2 100644
--- a/src/core/worker_loop_.ml
+++ b/src/core/worker_loop_.ml
@@ -21,8 +21,6 @@ exception No_more_tasks
 type 'st ops = {
   schedule: 'st -> task_full -> unit;
   get_next_task: 'st -> task_full;  (** @raise No_more_tasks *)
-  get_thread_state: unit -> 'st;
-      (** Access current thread's worker state from any worker *)
   around_task: 'st -> around_task;
   on_exn: 'st -> Exn_bt.t -> unit;
   runner: 'st -> Runner.t;
@@ -98,31 +96,28 @@ let with_handler (type st arg) ~(ops : st ops) (self : st) :
   let handler = Effect.Deep.{ retc = Fun.id; exnc = raise_with_bt; effc } in
   fun f -> Effect.Deep.match_with f () handler
 
-let worker_loop (type st) ~block_signals ~(ops : st ops) (self : st) : unit =
-  if block_signals then (
-    try
-      ignore
-        (Unix.sigprocmask SIG_BLOCK
-           [
-             Sys.sigterm;
-             Sys.sigpipe;
-             Sys.sigint;
-             Sys.sigchld;
-             Sys.sigalrm;
-             Sys.sigusr1;
-             Sys.sigusr2;
-           ]
-          : _ list)
-    with _ -> ()
-  );
+module type FINE_GRAINED_ARGS = sig
+  type st
 
-  let cur_fiber : fiber ref = ref _dummy_fiber in
-  let runner = ops.runner self in
-  TLS.set Runner.For_runner_implementors.k_cur_runner runner;
+  val ops : st ops
+  val st : st
+end
 
-  let (AT_pair (before_task, after_task)) = ops.around_task self in
+module Fine_grained (Args : FINE_GRAINED_ARGS) () = struct
+  open Args
+
+  let cur_fiber : fiber ref = ref _dummy_fiber
+  let runner = ops.runner st
+
+  type state =
+    | New
+    | Ready
+    | Torn_down
+
+  let state = ref New
 
   let run_task (task : task_full) : unit =
+    let (AT_pair (before_task, after_task)) = ops.around_task st in
     let fiber =
       match task with
       | T_start { fiber; _ } | T_resume { fiber; _ } -> fiber
@@ -136,32 +131,82 @@ let worker_loop (type st) ~block_signals ~(ops : st ops) (self : st) : unit =
     assert (task != _dummy_task);
     (try
        match task with
-       | T_start { fiber = _; f } -> with_handler ~ops self f
+       | T_start { fiber = _; f } -> with_handler ~ops st f
        | T_resume { fiber = _; k } ->
          (* this is already in an effect handler *)
          k ()
      with e ->
        let bt = Printexc.get_raw_backtrace () in
        let ebt = Exn_bt.make e bt in
-       ops.on_exn self ebt);
+       ops.on_exn st ebt);
 
     after_task runner _ctx;
 
     cur_fiber := _dummy_fiber;
     TLS.set k_cur_fiber _dummy_fiber
-  in
 
-  ops.before_start self;
+  let setup (type st) ~block_signals () : unit =
+    if !state <> New then invalid_arg "worker_loop.setup: not a new instance";
+    state := Ready;
 
-  let continue = ref true in
-  try
-    while !continue do
-      match ops.get_next_task self with
-      | task -> run_task task
+    if block_signals then (
+      try
+        ignore
+          (Unix.sigprocmask SIG_BLOCK
+             [
+               Sys.sigterm;
+               Sys.sigpipe;
+               Sys.sigint;
+               Sys.sigchld;
+               Sys.sigalrm;
+               Sys.sigusr1;
+               Sys.sigusr2;
+             ]
+            : _ list)
+      with _ -> ()
+    );
+
+    TLS.set Runner.For_runner_implementors.k_cur_runner runner;
+
+    ops.before_start st
+
+  let run ?(max_tasks = max_int) () : unit =
+    if !state <> Ready then invalid_arg "worker_loop.run: not setup";
+
+    let continue = ref true in
+    let n_tasks = ref 0 in
+    while !continue && !n_tasks < max_tasks do
+      match ops.get_next_task st with
+      | task ->
+        incr n_tasks;
+        run_task task
       | exception No_more_tasks -> continue := false
-    done;
-    ops.cleanup self
+    done
+
+  let teardown () =
+    if !state <> Torn_down then (
+      state := Torn_down;
+      cur_fiber := _dummy_fiber;
+      ops.cleanup st
+    )
+end
+
+let worker_loop (type st) ~block_signals ~(ops : st ops) (self : st) : unit =
+  let module FG =
+    Fine_grained
+      (struct
+        type nonrec st = st
+
+        let ops = ops
+        let st = self
+      end)
+      ()
+  in
+  FG.setup ~block_signals ();
+  try
+    FG.run ();
+    FG.teardown ()
   with exn ->
     let bt = Printexc.get_raw_backtrace () in
-    ops.cleanup self;
+    FG.teardown ();
     Printexc.raise_with_backtrace exn bt
diff --git a/src/core/worker_loop_.mli b/src/core/worker_loop_.mli
index 7098deb8..3041b0dd 100644
--- a/src/core/worker_loop_.mli
+++ b/src/core/worker_loop_.mli
@@ -26,7 +26,6 @@ exception No_more_tasks
 type 'st ops = {
   schedule: 'st -> task_full -> unit;
   get_next_task: 'st -> task_full;
-  get_thread_state: unit -> 'st;
   around_task: 'st -> around_task;
   on_exn: 'st -> Exn_bt.t -> unit;
   runner: 'st -> Runner.t;
@@ -34,4 +33,23 @@ type 'st ops = {
   cleanup: 'st -> unit;
 }
 
+module type FINE_GRAINED_ARGS = sig
+  type st
+
+  val ops : st ops
+  val st : st
+end
+
+module Fine_grained (_ : FINE_GRAINED_ARGS) () : sig
+  val setup : block_signals:bool -> unit -> unit
+  (** Just initialize the loop *)
+
+  val run : ?max_tasks:int -> unit -> unit
+  (** Run the loop until no task remains or until [max_tasks] tasks have been
+      run *)
+
+  val teardown : unit -> unit
+  (** Tear down the loop *)
+end
+
 val worker_loop : block_signals:bool -> ops:'st ops -> 'st -> unit
diff --git a/src/core/ws_pool.ml b/src/core/ws_pool.ml
index 1b95cd16..153f4f06 100644
--- a/src/core/ws_pool.ml
+++ b/src/core/ws_pool.ml
@@ -62,12 +62,6 @@ let k_worker_state : worker_state TLS.t = TLS.create ()
 let[@inline] get_current_worker_ () : worker_state option =
   TLS.get_opt k_worker_state
 
-let[@inline] get_current_worker_exn () : worker_state =
-  match TLS.get_exn k_worker_state with
-  | w -> w
-  | exception TLS.Not_set ->
-    failwith "Moonpool: get_current_runner was called from outside a pool."
-
 (** Try to wake up a waiter, if there's any. *)
 let[@inline] try_wake_someone_ (self : state) : unit =
   if self.n_waiting_nonzero then (
@@ -212,7 +206,6 @@ let worker_ops : worker_state WL.ops =
     WL.schedule = schedule_from_w;
     runner;
     get_next_task;
-    get_thread_state = get_current_worker_exn;
     around_task;
     on_exn;
     before_start;