Issue #7212 has been updated by fiddur (Fredrik Liljegren).


Here's a little more debug-info (not sure if it's needed, but anyhow...)

I tried the patch from #3187, increasing the stack size of fibers.  I confirmed that the patch is working on a normal recursing method (without lambda block), increasing recursability 4 times by setting 16kb stacksize.  That did NOT affect this bug at all, still on 11 levels of recursion.

Not knowing how it's implemented, I tried lambda-blocks without closure-behaviour; i.e. without using external variables, using just:
  def recursive
    -> do
      p "Block"
      subblock = recursive
      subblock.call
    end
  end

...but it's exactly the same.


I also tried without the lambda notation, just sending in a block to recursive method.  That got me up to level 250 on both 1.9.3-p194 and 1.9.2-p320.  That's using:
  def recursive(level=0, &block)
    p "Level #{level}"
    recursive(level+1) { block.call }
  end
  Fiber.new { recursive {} }.resume


Well, hope it helps.

----------------------------------------
Bug #7212: "stack level too deep" in Fiber much earlier in new versions of 1.9.3
https://bugs.ruby-lang.org/issues/7212#change-31486

Author: fiddur (Fredrik Liljegren)
Status: Assigned
Priority: Normal
Assignee: ko1 (Koichi Sasada)
Category: 
Target version: 
ruby -v: ruby 1.9.3p286 (2012-10-12 revision 37165) [x86_64-linux] (and others, see description)


I was getting SystemStackError in my application on some servers and not others; on all with 1.9.3-p286 and on some with p194, and on none with 1.9.2-head.  I boiled it down to this:


def recursive(level = 0)
  -> do
    p "In block #{level}"
    if level < 1000
      subblock = recursive(level + 1)
      subblock.call
    end
  end
end

p "Doing recursive call in a fiber"
Fiber.new { recursive.call }.resume


On server A, 1.9.3-p194 and 1.9.3-p286 got up to 11 levels of recursion, while 1.9.2-head got up to 97 levels.
On server B (without 1.9.2), 1.9.3-p194 got 55 levels while p286 still got 11 levels.

I don't know what changes are made, but I think 11 levels are way on the low side for many applications.

(My original problem was with a thin-server running rack-fiber_pool with em-synchrony getting too deep in a regexp in Addressable::URI.)


-- 
http://bugs.ruby-lang.org/