make sched_task more robust (#59669)

If the sched_task ever dies, we need to recreate a new one. Creating a
new one is very cheap, so it is unclear why we don't always do it this
way. But at least do it this way if it ever dies (e.g. from an untimely
InterruptException).

Fix #58689

Author: vtjnash

base/task.jl

@@ -1132,9 +1132,25 @@ function throwto(t::Task, @nospecialize exc)
     return try_yieldto(identity)
 end
 
-@inline function wait_forever()
+function wait_forever()
     while true
-        wait()
+        try
+            while true
+                wait()
+            end
+        catch e
+            local errs = stderr
+            # try to display the failure atomically
+            errio = IOContext(PipeBuffer(), errs::IO)
+            emphasize(errio, "Internal Task ")
+            display_error(errio, current_exceptions())
+            write(errs, errio)
+            # victimize another random Task also
+            if Threads.threadid() == 1 && isa(e, InterruptException) && isempty(Workqueue)
+                backend = repl_backend_task()
+                backend isa Task && throwto(backend, e)
+            end
+        end
     end
 end
 
@@ -1195,6 +1211,7 @@ function wait()
         # thread sleep logic.
         sched_task = get_sched_task()
         if ct !== sched_task
+            istaskdone(sched_task) && (sched_task = @task wait())
             return yieldto(sched_task)
         end
         task = ccall(:jl_task_get_next, Ref{Task}, (Any, Any, Any), trypoptask, W, checktaskempty)

contrib/juliac/juliac-buildscript.jl

@@ -66,35 +66,39 @@ let include_result = Base.include(Main, ARGS[1])
             end
         end
     end
-    #entrypoint(join, (Base.GenericIOBuffer{Memory{UInt8}}, Array{Base.SubString{String}, 1}, String))
-    #entrypoint(join, (Base.GenericIOBuffer{Memory{UInt8}}, Array{String, 1}, Char))
-    entrypoint(Base.task_done_hook, (Task,))
-    entrypoint(Base.wait, ())
-    entrypoint(Base.wait_forever, ())
-    entrypoint(Base.trypoptask, (Base.StickyWorkqueue,))
-    entrypoint(Base.checktaskempty, ())
-    if ARGS[3] == "true"
-        Base.Compiler.add_ccallable_entrypoints!()
-    end
-
-    # Export info about entrypoints and structs needed to create header files
-    if length(ARGS) >= 4
-        abi_export = ARGS[4]
-        open(abi_export, "w") do io
-            write_abi_metadata(io)
-        end
-    end
 end
 
 # Run the verifier in the current world (before build-script modifications),
 # so that error messages and types print in their usual way.
 Core.Compiler._verify_trim_world_age[] = Base.get_world_counter()
 
+# Apply hacks
+
 if Base.JLOptions().trim != 0
     include(joinpath(@__DIR__, "juliac-trim-base.jl"))
     include(joinpath(@__DIR__, "juliac-trim-stdlib.jl"))
 end
 
+#entrypoint(join, (Base.GenericIOBuffer{Memory{UInt8}}, Array{Base.SubString{String}, 1}, String))
+#entrypoint(join, (Base.GenericIOBuffer{Memory{UInt8}}, Array{String, 1}, Char))
+entrypoint(Base.task_done_hook, (Task,))
+entrypoint(Base.wait, ())
+entrypoint(Base.wait_forever, ())
+entrypoint(Base.trypoptask, (Base.StickyWorkqueue,))
+entrypoint(Base.checktaskempty, ())
+
+if ARGS[3] == "true"
+    Base.Compiler.add_ccallable_entrypoints!()
+end
+
+# Export info about entrypoints and structs needed to create header files
+if length(ARGS) >= 4
+    abi_export = ARGS[4]
+    open(abi_export, "w") do io
+        write_abi_metadata(io)
+    end
+end
+
 empty!(Core.ARGS)
 empty!(Base.ARGS)
 empty!(LOAD_PATH)

contrib/juliac/juliac-trim-base.jl

@@ -12,6 +12,7 @@ end
     depwarn(msg, funcsym; force::Bool=false) = nothing
     _assert_tostring(msg) = ""
     reinit_stdio() = nothing
+    wait_forever() = while true; wait(); end
     JuliaSyntax.enable_in_core!() = nothing
     init_active_project() = ACTIVE_PROJECT[] = nothing
     set_active_project(projfile::Union{AbstractString,Nothing}) = ACTIVE_PROJECT[] = projfile