From 40d61f55ac53e3cd2f229d0b032da03032e3d53d Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Thu, 7 Jan 2010 00:37:57 -0800 Subject: POSIX_MQ#notify block execution on message received This is implementation uses both a short-lived POSIX thread and a pre-spawned Ruby Thread in a manner that works properly under both Ruby 1.8 (green threads) and 1.9 (where Ruby Threads are POSIX threads). The short-lived POSIX thread will write a single "\0" byte to a pipe the Ruby Thread waits on. This operation is atomic on all platforms. Once the Ruby Thread is woken up from the pipe, it will execute th block given to it. This dual-thread implementation is inspired by the way glibc implements mq_notify(3) + SIGEV_THREAD under Linux where the kernel itself cannot directly spawn POSIX threads. --- lib/posix_mq.rb | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'lib') diff --git a/lib/posix_mq.rb b/lib/posix_mq.rb index 5e660ec..91f4140 100644 --- a/lib/posix_mq.rb +++ b/lib/posix_mq.rb @@ -26,7 +26,38 @@ class POSIX_MQ mq.close unless mq.closed? end end + end + # Executes the given block upon reception of the next message in an + # empty queue. If the message queue is not empty, then this block + # will only be fired after the queue is emptied and repopulated with + # one message. + # + # This block will only be executed upon the arrival of the + # first message and must be reset/reenabled for subsequent + # notifications. This block will execute in a separate Ruby + # Thread (and thus will safely have the GVL by default). + def notify(&block) + block.arity == 1 or + raise ArgumentError, "arity of notify block must be 1" + r, w = IO.pipe + thr = Thread.new(r, w, self) do |r, w, mq| + begin + begin + r.read(1) or raise Errno::EINTR + rescue Errno::EINTR, Errno::EAGAIN + retry + end + block.call(mq) + ensure + mq.notify_thread = nil + r.close rescue nil + w.close rescue nil + end + end + self.notify = w + self.notify_thread = thr + nil end end -- cgit v1.2.3-24-ge0c7