1 files changed, 64 insertions, 0 deletions

diff --git a/lib/unicorn/worker.rb b/lib/unicorn/worker.rb
index 1fb6a4a..e74a1c9 100644
--- a/lib/unicorn/worker.rb
+++ b/lib/unicorn/worker.rb
@@ -12,6 +12,7 @@ class Unicorn::Worker
   # :stopdoc:
   attr_accessor :nr, :switched
   attr_writer :tmp
+  attr_reader :to_io # IO.select-compatible
 
   PER_DROP = Raindrops::PAGE_SIZE / Raindrops::SIZE
   DROPS = []
@@ -23,6 +24,66 @@ class Unicorn::Worker
     @raindrop[@offset] = 0
     @nr = nr
     @tmp = @switched = false
+    @to_io, @master = Unicorn.pipe
+  end
+
+  def atfork_child # :nodoc:
+    # we _must_ close in child, parent just holds this open to signal
+    @master = @master.close
+  end
+
+  # master fakes SIGQUIT using this
+  def quit # :nodoc:
+    @master = @master.close if @master
+  end
+
+  # parent does not read
+  def atfork_parent # :nodoc:
+    @to_io = @to_io.close
+  end
+
+  # call a signal handler immediately without triggering EINTR
+  # We do not use the more obvious Process.kill(sig, $$) here since
+  # that signal delivery may be deferred.  We want to avoid signal delivery
+  # while the Rack app.call is running because some database drivers
+  # (e.g. ruby-pg) may cancel pending requests.
+  def fake_sig(sig) # :nodoc:
+    old_cb = trap(sig, "IGNORE")
+    old_cb.call
+  ensure
+    trap(sig, old_cb)
+  end
+
+  # master sends fake signals to children
+  def soft_kill(sig) # :nodoc:
+    case sig
+    when Integer
+      signum = sig
+    else
+      signum = Signal.list[sig.to_s] or
+          raise ArgumentError, "BUG: bad signal: #{sig.inspect}"
+    end
+    # writing and reading 4 bytes on a pipe is atomic on all POSIX platforms
+    # Do not care in the odd case the buffer is full, here.
+    @master.kgio_trywrite([signum].pack('l'))
+  rescue Errno::EPIPE
+    # worker will be reaped soon
+  end
+
+  # this only runs when the Rack app.call is not running
+  # act like a listener
+  def kgio_tryaccept # :nodoc:
+    case buf = @to_io.kgio_tryread(4)
+    when String
+      # unpack the buffer and trigger the signal handler
+      signum = buf.unpack('l')
+      fake_sig(signum[0])
+      # keep looping, more signals may be queued
+    when nil # EOF: master died, but we are at a safe place to exit
+      fake_sig(:QUIT)
+    when :wait_readable # keep waiting
+      return false
+    end while true # loop, as multiple signals may be sent
   end
 
   # worker objects may be compared to just plain Integers
@@ -49,8 +110,11 @@ class Unicorn::Worker
     end
   end
 
+  # called in both the master (reaping worker) and worker (SIGQUIT handler)
   def close # :nodoc:
     @tmp.close if @tmp
+    @master.close if @master
+    @to_io.close if @to_io
   end
 
   # :startdoc: