Revert "Merge pull request JuliaLang/julia#38405 from JuliaLang/vc/distributed_ts" (JuliaLang/julia#41722)

Also reverts "fixup to pull request JuliaLang/julia#38405 (JuliaLang/julia#41641)"

Seems to be causing hanging in CI testing.

This reverts commit 740a33a and this
reverts commit 5a1680533b461471f537f5f5d4ee3c2866b21e1f, reversing
changes made to 02807b279a5e6d5acaeb7095e4c0527e2a5c190e.

(cherry picked from commit bbc9429)

Author: vtjnash

src/cluster.jl

@@ -95,14 +95,13 @@ end
 @enum WorkerState W_CREATED W_CONNECTED W_TERMINATING W_TERMINATED
 mutable struct Worker
     id::Int
-    msg_lock::Threads.ReentrantLock # Lock for del_msgs, add_msgs, and gcflag
     del_msgs::Array{Any,1}
     add_msgs::Array{Any,1}
     gcflag::Bool
     state::WorkerState
-    c_state::Threads.Condition # wait for state changes, lock for state
-    ct_time::Float64           # creation time
-    conn_func::Any             # used to setup connections lazily
+    c_state::Condition      # wait for state changes
+    ct_time::Float64        # creation time
+    conn_func::Any          # used to setup connections lazily
 
     r_stream::IO
     w_stream::IO
@@ -134,7 +133,7 @@ mutable struct Worker
         if haskey(map_pid_wrkr, id)
             return map_pid_wrkr[id]
         end
-        w=new(id, Threads.ReentrantLock(), [], [], false, W_CREATED, Threads.Condition(), time(), conn_func)
+        w=new(id, [], [], false, W_CREATED, Condition(), time(), conn_func)
         w.initialized = Event()
         register_worker(w)
         w
@@ -144,16 +143,12 @@ mutable struct Worker
 end
 
 function set_worker_state(w, state)
-    lock(w.c_state) do
-        w.state = state
-        notify(w.c_state; all=true)
-    end
+    w.state = state
+    notify(w.c_state; all=true)
 end
 
 function check_worker_state(w::Worker)
-    lock(w.c_state)
     if w.state === W_CREATED
-        unlock(w.c_state)
         if !isclusterlazy()
             if PGRP.topology === :all_to_all
                 # Since higher pids connect with lower pids, the remote worker
@@ -173,8 +168,6 @@ function check_worker_state(w::Worker)
             errormonitor(t)
             wait_for_conn(w)
         end
-    else
-        unlock(w.c_state)
     end
 end
 
@@ -193,25 +186,13 @@ function exec_conn_func(w::Worker)
 end
 
 function wait_for_conn(w)
-    lock(w.c_state)
     if w.state === W_CREATED
-        unlock(w.c_state)
         timeout =  worker_timeout() - (time() - w.ct_time)
         timeout <= 0 && error("peer $(w.id) has not connected to $(myid())")
 
-        T = Threads.@spawn begin
-            sleep($timeout)
-            lock(w.c_state) do
-                notify(w.c_state; all=true)
-            end
-        end
-        errormonitor(T)
-        lock(w.c_state) do
-            wait(w.c_state)
-            w.state === W_CREATED && error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
-        end
-    else
-        unlock(w.c_state)
+        @async (sleep(timeout); notify(w.c_state; all=true))
+        wait(w.c_state)
+        w.state === W_CREATED && error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
     end
     nothing
 end
@@ -490,10 +471,6 @@ function addprocs_locked(manager::ClusterManager; kwargs...)
     # The `launch` method should add an object of type WorkerConfig for every
     # worker launched. It provides information required on how to connect
     # to it.
-
-    # FIXME: launched should be a Channel, launch_ntfy should be a Threads.Condition
-    # but both are part of the public interface. This means we currently can't use
-    # `Threads.@spawn` in the code below.
     launched = WorkerConfig[]
     launch_ntfy = Condition()
 
@@ -506,10 +483,7 @@ function addprocs_locked(manager::ClusterManager; kwargs...)
         while true
             if isempty(launched)
                 istaskdone(t_launch) && break
-                @async begin
-                    sleep(1)
-                    notify(launch_ntfy)
-                end
+                @async (sleep(1); notify(launch_ntfy))
                 wait(launch_ntfy)
             end
 
@@ -662,12 +636,7 @@ function create_worker(manager, wconfig)
         # require the value of config.connect_at which is set only upon connection completion
         for jw in PGRP.workers
             if (jw.id != 1) && (jw.id < w.id)
-                # wait for wl to join
-                lock(jw.c_state) do
-                    if jw.state === W_CREATED
-                        wait(jw.c_state)
-                    end
-                end
+                (jw.state === W_CREATED) && wait(jw.c_state)
                 push!(join_list, jw)
             end
         end
@@ -690,12 +659,7 @@ function create_worker(manager, wconfig)
         end
 
         for wl in wlist
-            lock(wl.c_state) do
-                if wl.state === W_CREATED
-                    # wait for wl to join
-                    wait(wl.c_state)
-                end
-            end
+            (wl.state === W_CREATED) && wait(wl.c_state)
             push!(join_list, wl)
         end
     end
@@ -712,11 +676,7 @@ function create_worker(manager, wconfig)
     @async manage(w.manager, w.id, w.config, :register)
     # wait for rr_ntfy_join with timeout
     timedout = false
-    @async begin
-        sleep($timeout)
-        timedout = true
-        put!(rr_ntfy_join, 1)
-    end
+    @async (sleep($timeout); timedout = true; put!(rr_ntfy_join, 1))
     wait(rr_ntfy_join)
     if timedout
         error("worker did not connect within $timeout seconds")

src/macros.jl

@@ -1,10 +1,14 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-let nextidx = Threads.Atomic{Int}(0)
+let nextidx = 0
     global nextproc
     function nextproc()
-        idx = Threads.atomic_add!(nextidx, 1)
-        return workers()[(idx % nworkers()) + 1]
+        p = -1
+        if p == -1
+            p = workers()[(nextidx % nworkers()) + 1]
+            nextidx += 1
+        end
+        p
     end
 end
 

src/managers.jl

@@ -160,7 +160,7 @@ function launch(manager::SSHManager, params::Dict, launched::Array, launch_ntfy:
     # Wait for all launches to complete.
     @sync for (i, (machine, cnt)) in enumerate(manager.machines)
         let machine=machine, cnt=cnt
-            @async try
+             @async try
                 launch_on_machine(manager, $machine, $cnt, params, launched, launch_ntfy)
             catch e
                 print(stderr, "exception launching on machine $(machine) : $(e)\n")

src/messages.jl

@@ -126,20 +126,22 @@ function flush_gc_msgs(w::Worker)
     if !isdefined(w, :w_stream)
         return
     end
-    lock(w.msg_lock) do
-        w.gcflag || return # early exit if someone else got to this
-        w.gcflag = false
-        msgs = w.add_msgs
-        w.add_msgs = Any[]
-        if !isempty(msgs)
-            remote_do(add_clients, w, msgs)
-        end
+    w.gcflag = false
+    new_array = Any[]
+    msgs = w.add_msgs
+    w.add_msgs = new_array
+    if !isempty(msgs)
+        remote_do(add_clients, w, msgs)
+    end
 
-        msgs = w.del_msgs
-        w.del_msgs = Any[]
-        if !isempty(msgs)
-            remote_do(del_clients, w, msgs)
-        end
+    # del_msgs gets populated by finalizers, so be very careful here about ordering of allocations
+    # XXX: threading requires this to be atomic
+    new_array = Any[]
+    msgs = w.del_msgs
+    w.del_msgs = new_array
+    if !isempty(msgs)
+        #print("sending delete of $msgs\n")
+        remote_do(del_clients, w, msgs)
     end
 end
 

src/remotecall.jl

@@ -247,42 +247,22 @@ function del_clients(pairs::Vector)
     end
 end
 
-# The task below is coalescing the `flush_gc_msgs` call
-# across multiple producers, see `send_del_client`,
-# and `send_add_client`.
-# XXX: Is this worth the additional complexity?
-#      `flush_gc_msgs` has to iterate over all connected workers.
-const any_gc_flag = Threads.Condition()
+const any_gc_flag = Condition()
 function start_gc_msgs_task()
-    errormonitor(
-        Threads.@spawn begin
-            while true
-                lock(any_gc_flag) do
-                    wait(any_gc_flag)
-                    flush_gc_msgs() # handles throws internally
-                end
-            end
-        end
-    )
+    errormonitor(@async while true
+        wait(any_gc_flag)
+        flush_gc_msgs()
+    end)
 end
 
-# Function can be called within a finalizer
 function send_del_client(rr)
     if rr.where == myid()
         del_client(rr)
     elseif id_in_procs(rr.where) # process only if a valid worker
         w = worker_from_id(rr.where)::Worker
-        msg = (remoteref_id(rr), myid())
-        # We cannot acquire locks from finalizers
-        Threads.@spawn begin
-            lock(w.msg_lock) do
-                push!(w.del_msgs, msg)
-                w.gcflag = true
-            end
-            lock(any_gc_flag) do
-                notify(any_gc_flag)
-            end
-        end
+        push!(w.del_msgs, (remoteref_id(rr), myid()))
+        w.gcflag = true
+        notify(any_gc_flag)
     end
 end
 
@@ -308,13 +288,9 @@ function send_add_client(rr::AbstractRemoteRef, i)
         # to the processor that owns the remote ref. it will add_client
         # itself inside deserialize().
         w = worker_from_id(rr.where)
-        lock(w.msg_lock) do
-            push!(w.add_msgs, (remoteref_id(rr), i))
-            w.gcflag = true
-        end
-        lock(any_gc_flag) do
-            notify(any_gc_flag)
-        end
+        push!(w.add_msgs, (remoteref_id(rr), i))
+        w.gcflag = true
+        notify(any_gc_flag)
     end
 end
 

test/distributed_exec.jl

@@ -1689,5 +1689,4 @@ include("splitrange.jl")
 # Run topology tests last after removing all workers, since a given
 # cluster at any time only supports a single topology.
 rmprocs(workers())
-include("threads.jl")
 include("topology.jl")