use atomic bool to check RNG initialization

src/lib.rs

@@ -5,8 +5,6 @@
 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
-
-
 #![no_std]
 
 #[cfg(any(

src/linux_android.rs

@@ -15,6 +15,9 @@ use std::fs::File;
 use std::io;
 use std::io::Read;
 use std::cell::RefCell;
+use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+
+static RNG_INIT: AtomicBool = ATOMIC_BOOL_INIT;
 
 enum RngSource {
     GetRandom,
@@ -44,7 +47,10 @@ pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
             } else {
                 // read one byte from "/dev/random" to ensure that
                 // OS RNG has initialized
-                File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
+                if !RNG_INIT.load(Ordering::Relaxed) {
+                    File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
+                    RNG_INIT.store(true, Ordering::Relaxed)
+                }
                 RngSource::Device(File::open("/dev/urandom")?)
             };
             Ok(s)
@@ -58,7 +64,6 @@ pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
 }
 
 fn is_getrandom_available() -> bool {
-    use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
     use std::sync::{Once, ONCE_INIT};
 
     static CHECKER: Once = ONCE_INIT;

src/netbsd.rs

@@ -13,6 +13,9 @@ use super::utils::use_init;
 use std::fs::File;
 use std::io::Read;
 use std::cell::RefCell;
+use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+
+static RNG_INIT: AtomicBool = ATOMIC_BOOL_INIT;
 
 thread_local!(static RNG_FILE: RefCell<Option<File>> = RefCell::new(None));
 
@@ -21,7 +24,10 @@ pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
         use_init(f, || {
             // read one byte from "/dev/random" to ensure that
             // OS RNG has initialized
-            File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
+            if !RNG_INIT.load(Ordering::Relaxed) {
+                File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
+                RNG_INIT.store(true, Ordering::Relaxed)
+            }
             File::open("/dev/urandom")
         }, |f| f.read_exact(dest))
     }).map_err(|_| Error::Unknown)