From: Brett Cannon <brett@python.org>
Date: Fri, 16 Nov 2012 02:39:36 +0000 (-0500)
Subject: Issue #15894: Document why we don't worry about re-acquiring the
X-Git-Tag: v3.4.0a1~2001
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e4710cfcedbecbd3bfa154c2586415ab5b6e28bc;p=thirdparty%2FPython%2Fcpython.git

Issue #15894: Document why we don't worry about re-acquiring the
global import lock after forking.
---

diff --git a/Python/import.c b/Python/import.c
index 2f71b97bc8b0..6882b570600b 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -202,8 +202,11 @@ _PyImport_ReInitLock(void)
     if (import_lock_level > 1) {
         /* Forked as a side effect of import */
         long me = PyThread_get_thread_ident();
-        PyThread_acquire_lock(import_lock, 0);
-        /* XXX: can the previous line fail? */
+        /* The following could fail if the lock is already held, but forking as
+           a side-effect of an import is a) rare, b) nuts, and c) difficult to
+           do thanks to the lock only being held when doing individual module
+           locks per import. */
+        PyThread_acquire_lock(import_lock, NOWAIT_LOCK);
         import_lock_thread = me;
         import_lock_level--;
     } else {