bpo-29386: Pass -1 to epoll_wait() when timeout is < -1 (GH-9040)
Although the kernel accepts any negative value for timeout, the
documented value to block indefinitely is -1.
This commit also makes the code similar to select.poll.poll().
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index 836af54..d86727a 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -1498,17 +1498,12 @@
int nfds, i;
PyObject *elist = NULL, *etuple = NULL;
struct epoll_event *evs = NULL;
- _PyTime_t timeout, ms, deadline;
+ _PyTime_t timeout = -1, ms = -1, deadline = 0;
if (self->epfd < 0)
return pyepoll_err_closed();
- if (timeout_obj == Py_None) {
- timeout = -1;
- ms = -1;
- deadline = 0; /* initialize to prevent gcc warning */
- }
- else {
+ if (timeout_obj != Py_None) {
/* epoll_wait() has a resolution of 1 millisecond, round towards
infinity to wait at least timeout seconds. */
if (_PyTime_FromSecondsObject(&timeout, timeout_obj,
@@ -1525,8 +1520,20 @@
PyErr_SetString(PyExc_OverflowError, "timeout is too large");
return NULL;
}
+ /* epoll_wait(2) treats all arbitrary negative numbers the same
+ for the timeout argument, but -1 is the documented way to block
+ indefinitely in the epoll_wait(2) documentation, so we set ms
+ to -1 if the value of ms is a negative number.
- deadline = _PyTime_GetMonotonicClock() + timeout;
+ Note that we didn't use INFTIM here since it's non-standard and
+ isn't available under Linux. */
+ if (ms < 0) {
+ ms = -1;
+ }
+
+ if (timeout >= 0) {
+ deadline = _PyTime_GetMonotonicClock() + timeout;
+ }
}
if (maxevents == -1) {