asyncio: Fix upstream issue 168: StreamReader.read(-1) from pipe may hang if data exceeds buffer limit.

1 files changed, 11 insertions, 6 deletions

diff --git a/Lib/asyncio/streams.py b/Lib/asyncio/streams.py
index 27d595f..e239248 100644
--- a/Lib/asyncio/streams.py
+++ b/Lib/asyncio/streams.py
@@ -419,12 +419,17 @@ class StreamReader:
             return b''
 
         if n < 0:
-            while not self._eof:
-                self._waiter = self._create_waiter('read')
-                try:
-                    yield from self._waiter
-                finally:
-                    self._waiter = None
+            # This used to just loop creating a new waiter hoping to
+            # collect everything in self._buffer, but that would
+            # deadlock if the subprocess sends more than self.limit
+            # bytes.  So just call self.read(self._limit) until EOF.
+            blocks = []
+            while True:
+                block = yield from self.read(self._limit)
+                if not block:
+                    break
+                blocks.append(block)
+            return b''.join(blocks)
         else:
             if not self._buffer and not self._eof:
                 self._waiter = self._create_waiter('read')