make parallel limiter specifically around work being done

Author: IanButterworth

base/precompilation.jl

@@ -920,7 +920,6 @@ function _precompilepkgs(pkgs::Vector{String},
                     circular = pkg in circular_deps
                     is_stale = !Base.isprecompiled(pkg; ignore_loaded=true, stale_cache, cachepath_cache, cachepaths, sourcepath, flags=cacheflags)
                     if !circular && is_stale
-                        Base.acquire(parallel_limiter)
                         is_project_dep = pkg in project_deps
 
                         # std monitoring
@@ -938,7 +937,6 @@ function _precompilepkgs(pkgs::Vector{String},
                         fancyprint && notify(first_started)
                         if interrupted_or_done.set
                             notify(was_processed[pkg_config])
-                            Base.release(parallel_limiter)
                             return
                         end
                         try
@@ -951,8 +949,13 @@ function _precompilepkgs(pkgs::Vector{String},
                                     # for extensions, any extension in our direct dependencies is one we have a right to load
                                     # for packages, we may load any extension (all possible triggers are accounted for above)
                                     loadable_exts = haskey(ext_to_parent, pkg) ? filter((dep)->haskey(ext_to_parent, dep), direct_deps[pkg]) : nothing
-                                    Base.compilecache(pkg, sourcepath, std_pipe, std_pipe, keep_loaded_modules;
+                                    Base.acquire(parallel_limiter)
+                                    try
+                                        Base.compilecache(pkg, sourcepath, std_pipe, std_pipe, keep_loaded_modules;
                                                       flags, cacheflags, loadable_exts)
+                                    finally
+                                        Base.release(parallel_limiter)
+                                    end
                                 end
                             end
                             if ret isa Base.PrecompilableError
@@ -984,7 +987,6 @@ function _precompilepkgs(pkgs::Vector{String},
                         finally
                             isopen(std_pipe.in) && close(std_pipe.in) # close pipe to end the std output monitor
                             wait(t_monitor)
-                            Base.release(parallel_limiter)
                         end
                     else
                         is_stale || (n_already_precomp += 1)