Do not stop the zstream loop for an interrupt

ext/zlib/zlib.c

@@ -1080,7 +1080,7 @@ zstream_run_func(struct zstream_run_args *args)
     uInt n;
 
     int err = Z_OK;
-    while (!args->interrupt) {
+    while (1) {
         n = z->stream.avail_out;
 
         err = (int)(VALUE)rb_ensure(zstream_run_once_begin, (VALUE)args, zstream_run_once_ensure, (VALUE)args);
@@ -1167,18 +1167,6 @@ zstream_run_try(VALUE value_arg)
 loop:
     err = zstream_run_func(args);
 
-    /* retry if no exception is thrown */
-    if (err == Z_OK && args->interrupt) {
-       args->interrupt = 0;
-
-       /* Retry only if both avail_in > 0 (more input to process) and avail_out > 0
-        * (output buffer has space). If avail_out == 0, the buffer is full and should
-        * be consumed by the caller first. If avail_in == 0, there's nothing more to process. */
-       if (z->stream.avail_in > 0 && z->stream.avail_out > 0) {
-          goto loop;
-       }
-    }
-
     if (flush != Z_FINISH && err == Z_BUF_ERROR && z->stream.avail_out > 0) {
         z->flags |= ZSTREAM_FLAG_IN_STREAM;
     }

test/zlib/test_zlib.rb

@@ -248,6 +248,37 @@ def test_close
       assert_raise(Zlib::Error) { z << "foo" }
       assert_raise(Zlib::Error) { z.reset }
     end
+
+    # An interrupt must neither raise Zlib::BufError on a deflate call that
+    # already consumed all its input, nor stop Zlib::Deflate#finish before the
+    # stream ends.
+    def test_thread_wakeup_interrupt
+      pend 'fails' if RUBY_ENGINE == 'truffleruby'
+
+      content = SecureRandom.random_bytes(256 * 1024)
+      outputs = []
+
+      thr = Thread.new do
+        100.times do
+          z = Zlib::Deflate.new
+          outputs << (z.deflate(content) << z.finish)
+          z.close
+        end
+      end
+
+      while thr.alive?
+        begin
+          thr.wakeup
+        rescue ThreadError
+        end
+        Thread.pass
+      end
+      thr.join
+
+      outputs.each do |output|
+        assert_equal(content, Zlib::Inflate.inflate(output))
+      end
+    end
   end
 
   class TestZlibInflate < Test::Unit::TestCase