Random: RandomDevice() share /dev/[u]random file handles (#27936)

stdlib/Random/src/RNGs.jl

@@ -19,24 +19,24 @@ if Sys.iswindows()
     end
 else # !windows
     struct RandomDevice <: AbstractRNG
-        file::IOStream
         unlimited::Bool
 
-        RandomDevice(; unlimited::Bool=true) =
-            new(open(unlimited ? "/dev/urandom" : "/dev/random"), unlimited)
+        RandomDevice(; unlimited::Bool=true) = new(unlimited)
     end
 
-    rand(rd::RandomDevice, sp::SamplerBoolBitInteger) = read( rd.file, sp[])
+    rand(rd::RandomDevice, sp::SamplerBoolBitInteger) = read(getfile(rd), sp[])
 
-    function serialize(s::AbstractSerializer, rd::RandomDevice)
-        Serialization.serialize_type(s, typeof(rd))
-        serialize(s, rd.unlimited)
-    end
-    function deserialize(s::AbstractSerializer, t::Type{RandomDevice})
-        unlimited = deserialize(s)
-        return RandomDevice(unlimited=unlimited)
+    function getfile(rd::RandomDevice)
+        devrandom = rd.unlimited ? DEV_URANDOM : DEV_RANDOM
+        # TODO: there is a data-race, this can leak up to nthreads() copies of the file descriptors,
+        # so use a "thread-once" utility once available
+        isassigned(devrandom) || (devrandom[] = open(rd.unlimited ? "/dev/urandom" : "/dev/random"))
+        devrandom[]
     end
 
+    const DEV_RANDOM  = Ref{IOStream}()
+    const DEV_URANDOM = Ref{IOStream}()
+
 end # os-test
 
 # NOTE: this can't be put within the if-else block above
@@ -48,7 +48,7 @@ for T in (Bool, BitInteger_types...)
             A
         end
     else
-        @eval rand!(rd::RandomDevice, A::Array{$T}, ::SamplerType{$T}) = read!(rd.file, A)
+        @eval rand!(rd::RandomDevice, A::Array{$T}, ::SamplerType{$T}) = read!(getfile(rd), A)
     end
 end
 

stdlib/Random/src/Random.jl

@@ -16,10 +16,8 @@ using Base.GMP: Limb
 
 using Base: BitInteger, BitInteger_types, BitUnsigned, require_one_based_indexing
 
-import Base: copymutable, copy, copy!, ==, hash, convert
-using Serialization
-import Serialization: serialize, deserialize
-import Base: rand, randn
+import Base: copymutable, copy, copy!, ==, hash, convert,
+             rand, randn
 
 export rand!, randn!,
        randexp, randexp!,