[Qemu-devel] [PATCH 02/17] iotests: iotests.py: prevent deadlock in subprocess

[Roman Kagan]

A subprocess whose std{out,err} is subprocess.PIPE may block writing its
output, so .wait() should not be called on it until the pipes are read
completely on the caller's side.

Subprocess.communicate takes care of this.

Signed-off-by: Roman Kagan <address@hidden>
---
 tests/qemu-iotests/iotests.py | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index b25d48a91b..e2abf0cb53 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -104,20 +104,20 @@ def qemu_img_pipe(*args):
     subp = subprocess.Popen(qemu_img_args + list(args),
                             stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
-    exitcode = subp.wait()
-    if exitcode < 0:
-        sys.stderr.write('qemu-img received signal %i: %s\n' % (-exitcode, ' 
'.join(qemu_img_args + list(args))))
-    return subp.communicate()[0]
+    output = subp.communicate()[0]
+    if subp.returncode < 0:
+        sys.stderr.write('qemu-img received signal %i: %s\n' % 
(-subp.returncode, ' '.join(qemu_img_args + list(args))))
+    return output
 
 def qemu_io(*args):
     '''Run qemu-io and return the stdout data'''
     args = qemu_io_args + list(args)
     subp = subprocess.Popen(args, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
-    exitcode = subp.wait()
-    if exitcode < 0:
-        sys.stderr.write('qemu-io received signal %i: %s\n' % (-exitcode, ' 
'.join(args)))
-    return subp.communicate()[0]
+    output = subp.communicate()[0]
+    if subp.returncode < 0:
+        sys.stderr.write('qemu-io received signal %i: %s\n' % 
(-subp.returncode, ' '.join(args)))
+    return output
 
 
 class QemuIoInteractive:
-- 
2.14.3