Provide a sanity check during PyThreadState_DeleteCurrent() and
PyThreadState_Delete() to avoid an infinite loop when the tstate list
is messed up and has somehow becomes circular and does not contain the
current thread.
I don't know how this happens but it does, *very* rarely. On more than
one hardware platform. I have not been able to reproduce it manually.
Attaching to a process where its happening: it has always been in an
infinite loop over a single element tstate list that is not the tstate
we're looking to delete. It has been in t_bootstrap()'s call to
PyThreadState_DeleteCurrent() as a pthread is exiting.
diff --git a/Python/pystate.c b/Python/pystate.c
index 086789d..36b06d6 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -240,6 +240,7 @@
{
PyInterpreterState *interp;
PyThreadState **p;
+ PyThreadState *prev_p = NULL;
if (tstate == NULL)
Py_FatalError("PyThreadState_Delete: NULL tstate");
interp = tstate->interp;
@@ -252,6 +253,15 @@
"PyThreadState_Delete: invalid tstate");
if (*p == tstate)
break;
+ if (*p == prev_p)
+ Py_FatalError(
+ "PyThreadState_Delete: small circular list(!)"
+ " and tstate not found.");
+ prev_p = *p;
+ if ((*p)->next == interp->tstate_head)
+ Py_FatalError(
+ "PyThreadState_Delete: circular list(!) and"
+ " tstate not found.");
}
*p = tstate->next;
HEAD_UNLOCK();