From: Brian Watling <bwatling@fb.com>
Date: Wed, 5 Nov 2014 22:50:37 +0000 (-0800)
Subject: Fix crashes in readRandomDevice()
X-Git-Tag: v0.22.0~195
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=100ebad746bbc310bb56bfd1c11e6054970ab873;p=folly.git

Fix crashes in readRandomDevice()

Summary: The comment in readRandomDevice() lies - the PCHECK fails with "Bad file descriptor" in some tests. This is most likely due to a race where a background thread is calling readRandomDevice() while the main thread shuts down. Another possibility is bad destruction order, where rnadomDevice is destroyed before some other static object whose destructor calls readRandomDevice(). Either way, this fixes it without having to chace down every instance.

Test Plan: run unit tests

Reviewed By: meyering@fb.com

Subscribers: antonl, trunkagent, meyering, simpkins, njormrod, folly-diffs@, tao-eng@

FB internal diff: D1660903

Signature: t1:1660903:1415215895:7f1f96ab7416b45c4dc18e78173fb59eb27bd03b
---

diff --git a/folly/Random.cpp b/folly/Random.cpp
index 533ac407..4ed578c3 100644
--- a/folly/Random.cpp
+++ b/folly/Random.cpp
@@ -31,8 +31,9 @@ namespace folly {
 namespace {
 
 void readRandomDevice(void* data, size_t size) {
-  // Keep it open for the duration of the program
-  static File randomDevice("/dev/urandom");
+  // Keep it open for the duration of the program. Note that we leak the File
+  // to ensure the file is indeed open for the duration of the program.
+  static File& randomDevice = *new File("/dev/urandom");
   auto bytesRead = readFull(randomDevice.fd(), data, size);
   PCHECK(bytesRead >= 0 && size_t(bytesRead) == size);
 }