From: Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org>
To: rainbows-talk-GrnCvJ7WPxnNLxjTenLetw@public.gmane.org
Subject: [PATCH] possible MRI 1.8 thread fix to avoid blocking accept()
Date: Mon, 21 Dec 2009 16:54:21 -0800 [thread overview]
Message-ID: <20091222005421.GA23044@dcvr.yhbt.net> (raw)
In-Reply-To: <20091221221002.GA12277-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
Under MRI 1.8, listen sockets do not appear to have the
nonblocking I/O flag on by default, nor does it set the
nonblocking I/O flag when calling #accept (but it does
when using #accept_nonblock, of course).
Normally this is not a problem even when using green threads
since MRI will internally select(2) on the file descriptor
before attempting a blocking (and immediately successful)
accept(2).
However, when sharing a listen descriptor across multiple
processes, spurious wakeups are likely to occur, causing
multiple processes may be woken up when a single client
connects.
This causes a problem because accept(2)-ing on multiple
threads/processes for a single connection causes blocking accepts in
multiple processes, leading to stalled green threads.
This is not an issue under 1.9 where a blocking accept() call
unlocks the GVL to let other threads run.
---
I just pushed this out to git://git.bogomips.org/rainbows.git, too.
Testers appreciated, thanks.
Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org> wrote:
> I've heard (privately) about issues with accept() somehow blocking the
> entire worker process under 1.8. Obviously this really should not
> happen, but I'm unable to reproduce it myself.
lib/rainbows/base.rb | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/lib/rainbows/base.rb b/lib/rainbows/base.rb
index 211b41c..4a4d076 100644
--- a/lib/rainbows/base.rb
+++ b/lib/rainbows/base.rb
@@ -14,6 +14,12 @@ module Rainbows
super(worker)
G.tmp = worker.tmp
+ # avoid spurious wakeups and blocking-accept() with 1.8 green threads
+ if RUBY_VERSION.to_f < 1.8
+ require "io/nonblock"
+ LISTENERS.each { |l| l.nonblock = true }
+ end
+
# we're don't use the self-pipe mechanism in the Rainbows! worker
# since we don't defer reopening logs
HttpServer::SELF_PIPE.each { |x| x.close }.clear
--
Eric Wong
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next prev parent reply other threads:[~2009-12-22 0:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-21 22:10 possible ThreadSpawn + Ruby 1.8 issues Eric Wong
[not found] ` <20091221221002.GA12277-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
2009-12-22 0:54 ` Eric Wong [this message]
[not found] ` <20091222005421.GA23044-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
2009-12-22 20:50 ` [PATCH 2/1] fix Ruby 1.8 detection for (possible) green thread fix Eric Wong
[not found] ` <20091222205008.GA11119-yBiyF41qdooeIZ0/mPfg9Q@public.gmane.org>
2009-12-22 21:34 ` [PATCH 3/1] base: fix constant resolution under 1.8 for 1.8 bugfix Eric Wong
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