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Scale back IO#select patch so it mutexes only zero-timeout calls

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commit fd3cb2fe0b128fed2def2bd3e9957d473a9c879c 1 parent be59921
@dazuma dazuma authored
Showing with 11 additions and 3 deletions.
  1. +11 −3 lib/net/ssh/ruby_compat.rb
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14 lib/net/ssh/ruby_compat.rb
@@ -14,9 +14,9 @@ module Net; module SSH
# for different ruby implementations.
class Compat
- # A workaround for an IO#select threading bug in MRI 1.8.
+ # A workaround for an IO#select threading bug in certain versions of MRI 1.8.
# See: http://net-ssh.lighthouseapp.com/projects/36253/tickets/1-ioselect-threading-bug-in-ruby-18
- # Also: http://redmine.ruby-lang.org/issues/show/1993
+ # The root issue is documented here: http://redmine.ruby-lang.org/issues/show/1993
if RUBY_VERSION >= '1.9' || RUBY_PLATFORM == 'java'
def self.io_select(*params)
IO.select(*params)
@@ -24,7 +24,15 @@ def self.io_select(*params)
else
SELECT_MUTEX = Mutex.new
def self.io_select(*params)
- SELECT_MUTEX.synchronize do
+ # It should be safe to wrap calls in a mutex when the timeout is 0
+ # (that is, the call is not supposed to block).
+ # We leave blocking calls unprotected to avoid causing deadlocks.
+ # This should still catch the main case for Capistrano users.
+ if params[3] == 0
+ SELECT_MUTEX.synchronize do
+ IO.select(*params)
+ end
+ else
IO.select(*params)
end
end
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