[Python-checkins] cpython: Issue #15894: Document why we don't worry about re-acquiring the

[brett.cannon]

http://hg.python.org/cpython/rev/bd853311ffe0
changeset:   80451:bd853311ffe0
user:        Brett Cannon <brett at python.org>
date:        Thu Nov 15 21:39:36 2012 -0500
summary:
  Issue #15894: Document why we don't worry about re-acquiring the
global import lock after forking.

files:
  Python/import.c |  7 +++++--
  1 files changed, 5 insertions(+), 2 deletions(-)


diff --git a/Python/import.c b/Python/import.c
--- a/Python/import.c
+++ b/Python/import.c
@@ -202,8 +202,11 @@
     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 {

-- 
Repository URL: http://hg.python.org/cpython