make _min_enabled_level Threads.Atomic

Author: IanButterworth

base/logging/logging.jl

@@ -132,6 +132,7 @@ isless(a::LogLevel, b::LogLevel) = isless(a.level, b.level)
 +(level::LogLevel, inc::Integer) = LogLevel(level.level+inc)
 -(level::LogLevel, inc::Integer) = LogLevel(level.level-inc)
 convert(::Type{LogLevel}, level::Integer) = LogLevel(level)
+convert(::Type{Int32}, level::LogLevel) = level.level
 
 """
     BelowMinLevel
@@ -171,7 +172,7 @@ Alias for [`LogLevel(1_000_001)`](@ref LogLevel).
 const AboveMaxLevel = LogLevel( 1000001)
 
 # Global log limiting mechanism for super fast but inflexible global log limiting.
-const _min_enabled_level = Ref{LogLevel}(Debug)
+const _min_enabled_level = Threads.Atomic{Int32}(Debug)
 
 function show(io::IO, level::LogLevel)
     if     level == BelowMinLevel  print(io, "BelowMinLevel")
@@ -394,7 +395,7 @@ function logmsg_code(_module, file, line, level, message, exs...)
             level = $level
             # simplify std_level code emitted, if we know it is one of our global constants
             std_level = $(level isa Symbol ? :level : :(level isa $LogLevel ? level : convert($LogLevel, level)::$LogLevel))
-            if std_level >= $(_min_enabled_level)[]
+            if std_level.level >= _min_enabled_level[]
                 group = $(log_data._group)
                 _module = $(log_data._module)
                 logger = $(current_logger_for_env)(std_level, group, _module)