quiet spurious wakeups for accept() in Thread* models

Under all MRI 1.8, a blocking Socket#accept Ruby method (needs
to[1]) translate to a non-blocking accept(2) system call that may
wake up threads/processes unnecessarily.  Unfortunately, we
failed to trap and ignore EAGAIN in those cases.

This issue did not affect Ruby 1.9 running under modern Linux
kernels where a _blocking_ accept(2) system call is not (easily,
at least) susceptible to spurious wakeups.  Non-Linux systems
running Ruby 1.9 may be affected.

[1] - using a blocking accept(2) on a shared socket with
      green threads is dangerous, as noted in
      commit ee7fe220ccbc991e1e7cbe982caf48e3303274c7
      (and commit 451ca6997b4f298b436605b7f0af75f369320425)

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/rainbows.rb b/lib/rainbows.rb
index d3a3e7d..9260649 100644
--- a/lib/rainbows.rb
+++ b/lib/rainbows.rb
@@ -60,6 +60,13 @@ module Rainbows
 
     # returns nil if accept fails
     if defined?(Fcntl::FD_CLOEXEC)
+      def sync_accept(sock)
+        rv = sock.accept
+        rv.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
+        rv
+      rescue Errno::EAGAIN, Errno::ECONNABORTED, Errno::EINTR
+      end
+
       def accept(sock)
         rv = sock.accept_nonblock
         rv.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
@@ -67,6 +74,11 @@ module Rainbows
       rescue Errno::EAGAIN, Errno::ECONNABORTED
       end
     else
+      def sync_accept(sock)
+        sock.accept
+      rescue Errno::EAGAIN, Errno::ECONNABORTED, Errno::EINTR
+      end
+
       def accept(sock)
         sock.accept_nonblock
       rescue Errno::EAGAIN, Errno::ECONNABORTED