SERVER-5140: avoid a bug in SCons with subprocess.Popen

SCons overrides the subprocess module with its own custom implementation
(forked from an earlier version of Python, but with some patches).
SCons' implementation acquires a lock but does not release it during
Popen() if the command being executed cannot be found. The next
invocation of Popen() will hang indefinitely attempting to acquire the
lock.

Moving smoke_python_name() to a python module (i.e. out of the
SCons-managed files) causes "import subprocess" to find the actual,
system-installed subprocess module, which does not contain the buggy
locking.

2 files changed, 25 insertions, 25 deletions

diff --git a/SConstruct b/SConstruct
index dbe95a36b4a..e536f8a03ca 100644
--- a/SConstruct
+++ b/SConstruct
@@ -817,29 +817,6 @@ def add_exe(target):
         return target + ".exe"
     return target
 
-def smoke_python_name():
-    # if this script is being run by py2.5 or greater,
-    # then we assume that "python" points to a 2.5 or
-    # greater python VM. otherwise, explicitly use 2.5
-    # which we assume to be installed.
-    import subprocess
-    version = re.compile(r'[Pp]ython ([\d\.]+)', re.MULTILINE)
-    binaries = ['python2.5', 'python2.6', 'python2.7', 'python25', 'python26', 'python27', 'python']
-    for binary in binaries:
-        try:
-            # py-2.4 compatible replacement for shell backticks
-            out, err = subprocess.Popen([binary, '-V'], stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
-            for stream in (out, err):
-                match = version.search(stream)
-                if match:
-                    versiontuple = tuple(map(int, match.group(1).split('.')))
-                    if versiontuple >= (2, 5):
-                        return binary
-        except:
-            pass
-    # if that all fails, fall back to "python"
-    return "python"
-
 def setupBuildInfoFile( outFile ):
     version = utils.getGitVersion()
     if len(moduleNames) > 0:
@@ -1253,7 +1230,7 @@ def addSmoketest( name, deps ):
         else:
             target = name[5].lower() + name[6:]
 
-    addTest(name, deps, [ smoke_python_name() + " buildscripts/smoke.py " + " ".join(smokeFlags) + ' ' + target ])
+    addTest(name, deps, [ utils.smoke_python_name() + " buildscripts/smoke.py " + " ".join(smokeFlags) + ' ' + target ])
 
 addSmoketest( "smoke", [ add_exe( "test" ) ] )
 addSmoketest( "smokePerf", [ "perftest" ]  )
@@ -1651,7 +1628,7 @@ def build_and_test_client(env, target, source):
 
     call(scons_command + ["libmongoclient.a", "clientTests"], cwd=installDir)
 
-    return bool(call([smoke_python_name(), "buildscripts/smoke.py",
+    return bool(call([utils.smoke_python_name(), "buildscripts/smoke.py",
                       "--test-path", installDir, "client"]))
 env.Alias("clientBuild", [mongod, installDir], [build_and_test_client])
 env.AlwaysBuild("clientBuild")
diff --git a/buildscripts/utils.py b/buildscripts/utils.py
index 8021d8779da..91409c7db70 100644
--- a/buildscripts/utils.py
+++ b/buildscripts/utils.py
@@ -134,3 +134,26 @@ def didMongodStart( port=27017 , timeout=20 ):
             timeout = timeout - 1
     return False
 
+def smoke_python_name():
+    # if this script is being run by py2.5 or greater,
+    # then we assume that "python" points to a 2.5 or
+    # greater python VM. otherwise, explicitly use 2.5
+    # which we assume to be installed.
+    import subprocess
+    version = re.compile(r'[Pp]ython ([\d\.]+)', re.MULTILINE)
+    binaries = ['python2.5', 'python2.6', 'python2.7', 'python25', 'python26', 'python27', 'python']
+    for binary in binaries:
+        try:
+            # py-2.4 compatible replacement for shell backticks
+            out, err = subprocess.Popen([binary, '-V'], stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
+            for stream in (out, err):
+                match = version.search(stream)
+                if match:
+                    versiontuple = tuple(map(int, match.group(1).split('.')))
+                    if versiontuple >= (2, 5):
+                        return binary
+        except:
+            pass
+    # if that all fails, fall back to "python"
+    return "python"
+