bpo-41710: Add private _PyDeadline_Get() function (GH-28674)

Add a private C API for deadlines: add _PyDeadline_Init() and
_PyDeadline_Get() functions.

* Add _PyTime_Add() and _PyTime_Mul() functions which compute t1+t2
  and t1*t2 and clamp the result on overflow.
* _PyTime_MulDiv() now uses _PyTime_Add() and _PyTime_Mul().

7 files changed, 83 insertions, 68 deletions

diff --git a/Modules/_queuemodule.c b/Modules/_queuemodule.c
index b6769e6..eb61349 100644
--- a/Modules/_queuemodule.c
+++ b/Modules/_queuemodule.c
@@ -182,7 +182,7 @@ _queue.SimpleQueue.get
     cls: defining_class
     /
     block: bool = True
-    timeout: object = None
+    timeout as timeout_obj: object = None
 
 Remove and return an item from the queue.
 
@@ -198,11 +198,11 @@ in that case).
 
 static PyObject *
 _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls,
-                            int block, PyObject *timeout)
-/*[clinic end generated code: output=1969aefa7db63666 input=5fc4d56b9a54757e]*/
+                            int block, PyObject *timeout_obj)
+/*[clinic end generated code: output=5c2cca914cd1e55b input=5b4047bfbc645ec1]*/
 {
     _PyTime_t endtime = 0;
-    _PyTime_t timeout_val;
+    _PyTime_t timeout;
     PyObject *item;
     PyLockStatus r;
     PY_TIMEOUT_T microseconds;
@@ -211,24 +211,25 @@ _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls,
         /* Non-blocking */
         microseconds = 0;
     }
-    else if (timeout != Py_None) {
+    else if (timeout_obj != Py_None) {
         /* With timeout */
-        if (_PyTime_FromSecondsObject(&timeout_val,
-                                      timeout, _PyTime_ROUND_CEILING) < 0)
+        if (_PyTime_FromSecondsObject(&timeout,
+                                      timeout_obj, _PyTime_ROUND_CEILING) < 0) {
             return NULL;
-        if (timeout_val < 0) {
+        }
+        if (timeout < 0) {
             PyErr_SetString(PyExc_ValueError,
                             "'timeout' must be a non-negative number");
             return NULL;
         }
-        microseconds = _PyTime_AsMicroseconds(timeout_val,
+        microseconds = _PyTime_AsMicroseconds(timeout,
                                               _PyTime_ROUND_CEILING);
         if (microseconds > PY_TIMEOUT_MAX) {
             PyErr_SetString(PyExc_OverflowError,
                             "timeout value is too large");
             return NULL;
         }
-        endtime = _PyTime_GetMonotonicClock() + timeout_val;
+        endtime = _PyDeadline_Init(timeout);
     }
     else {
         /* Infinitely blocking */
@@ -247,6 +248,7 @@ _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls,
             r = PyThread_acquire_lock_timed(self->lock, microseconds, 1);
             Py_END_ALLOW_THREADS
         }
+
         if (r == PY_LOCK_INTR && Py_MakePendingCalls() < 0) {
             return NULL;
         }
@@ -258,12 +260,15 @@ _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls,
             return NULL;
         }
         self->locked = 1;
+
         /* Adjust timeout for next iteration (if any) */
-        if (endtime > 0) {
-            timeout_val = endtime - _PyTime_GetMonotonicClock();
-            microseconds = _PyTime_AsMicroseconds(timeout_val, _PyTime_ROUND_CEILING);
+        if (microseconds > 0) {
+            timeout = _PyDeadline_Get(endtime);
+            microseconds = _PyTime_AsMicroseconds(timeout,
+                                                  _PyTime_ROUND_CEILING);
         }
     }
+
     /* BEGIN GIL-protected critical section */
     assert(self->lst_pos < PyList_GET_SIZE(self->lst));
     item = simplequeue_pop_item(self);
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 411314f..fedb35b 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -949,8 +949,9 @@ _ssl__SSLSocket_do_handshake_impl(PySSLSocket *self)
 
     timeout = GET_SOCKET_TIMEOUT(sock);
     has_timeout = (timeout > 0);
-    if (has_timeout)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (has_timeout) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     /* Actually negotiate SSL connection */
     /* XXX If SSL_do_handshake() returns 0, it's also a failure. */
@@ -965,7 +966,7 @@ _ssl__SSLSocket_do_handshake_impl(PySSLSocket *self)
             goto error;
 
         if (has_timeout)
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
 
         if (err.ssl == SSL_ERROR_WANT_READ) {
             sockstate = PySSL_select(sock, 0, timeout);
@@ -2326,8 +2327,9 @@ _ssl__SSLSocket_write_impl(PySSLSocket *self, Py_buffer *b)
 
     timeout = GET_SOCKET_TIMEOUT(sock);
     has_timeout = (timeout > 0);
-    if (has_timeout)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (has_timeout) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     sockstate = PySSL_select(sock, 1, timeout);
     if (sockstate == SOCKET_HAS_TIMED_OUT) {
@@ -2354,8 +2356,9 @@ _ssl__SSLSocket_write_impl(PySSLSocket *self, Py_buffer *b)
         if (PyErr_CheckSignals())
             goto error;
 
-        if (has_timeout)
-            timeout = deadline - _PyTime_GetMonotonicClock();
+        if (has_timeout) {
+            timeout = _PyDeadline_Get(deadline);
+        }
 
         if (err.ssl == SSL_ERROR_WANT_READ) {
             sockstate = PySSL_select(sock, 0, timeout);
@@ -2494,7 +2497,7 @@ _ssl__SSLSocket_read_impl(PySSLSocket *self, Py_ssize_t len,
     timeout = GET_SOCKET_TIMEOUT(sock);
     has_timeout = (timeout > 0);
     if (has_timeout)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+        deadline = _PyDeadline_Init(timeout);
 
     do {
         PySSL_BEGIN_ALLOW_THREADS
@@ -2506,8 +2509,9 @@ _ssl__SSLSocket_read_impl(PySSLSocket *self, Py_ssize_t len,
         if (PyErr_CheckSignals())
             goto error;
 
-        if (has_timeout)
-            timeout = deadline - _PyTime_GetMonotonicClock();
+        if (has_timeout) {
+            timeout = _PyDeadline_Get(deadline);
+        }
 
         if (err.ssl == SSL_ERROR_WANT_READ) {
             sockstate = PySSL_select(sock, 0, timeout);
@@ -2592,8 +2596,9 @@ _ssl__SSLSocket_shutdown_impl(PySSLSocket *self)
 
     timeout = GET_SOCKET_TIMEOUT(sock);
     has_timeout = (timeout > 0);
-    if (has_timeout)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (has_timeout) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     while (1) {
         PySSL_BEGIN_ALLOW_THREADS
@@ -2626,8 +2631,9 @@ _ssl__SSLSocket_shutdown_impl(PySSLSocket *self)
             continue;
         }
 
-        if (has_timeout)
-            timeout = deadline - _PyTime_GetMonotonicClock();
+        if (has_timeout) {
+            timeout = _PyDeadline_Get(deadline);
+        }
 
         /* Possibly retry shutdown until timeout or failure */
         if (err.ssl == SSL_ERROR_WANT_READ)
diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index fa7e6d0..543d82d 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -84,13 +84,12 @@ lock_dealloc(lockobject *self)
 static PyLockStatus
 acquire_timed(PyThread_type_lock lock, _PyTime_t timeout)
 {
-    PyLockStatus r;
     _PyTime_t endtime = 0;
-
     if (timeout > 0) {
-        endtime = _PyTime_GetMonotonicClock() + timeout;
+        endtime = _PyDeadline_Init(timeout);
     }
 
+    PyLockStatus r;
     do {
         _PyTime_t microseconds;
         microseconds = _PyTime_AsMicroseconds(timeout, _PyTime_ROUND_CEILING);
@@ -114,7 +113,7 @@ acquire_timed(PyThread_type_lock lock, _PyTime_t timeout)
             /* If we're using a timeout, recompute the timeout after processing
              * signals, since those can take time.  */
             if (timeout > 0) {
-                timeout = endtime - _PyTime_GetMonotonicClock();
+                timeout = _PyDeadline_Get(endtime);
 
                 /* Check for negative values, since those mean block forever.
                  */
diff --git a/Modules/clinic/_queuemodule.c.h b/Modules/clinic/_queuemodule.c.h
index d952256..22d2e99 100644
--- a/Modules/clinic/_queuemodule.c.h
+++ b/Modules/clinic/_queuemodule.c.h
@@ -139,7 +139,7 @@ PyDoc_STRVAR(_queue_SimpleQueue_get__doc__,
 
 static PyObject *
 _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls,
-                            int block, PyObject *timeout);
+                            int block, PyObject *timeout_obj);
 
 static PyObject *
 _queue_SimpleQueue_get(simplequeueobject *self, PyTypeObject *cls, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
@@ -148,13 +148,13 @@ _queue_SimpleQueue_get(simplequeueobject *self, PyTypeObject *cls, PyObject *con
     static const char * const _keywords[] = {"block", "timeout", NULL};
     static _PyArg_Parser _parser = {"|pO:get", _keywords, 0};
     int block = 1;
-    PyObject *timeout = Py_None;
+    PyObject *timeout_obj = Py_None;
 
     if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
-        &block, &timeout)) {
+        &block, &timeout_obj)) {
         goto exit;
     }
-    return_value = _queue_SimpleQueue_get_impl(self, cls, block, timeout);
+    return_value = _queue_SimpleQueue_get_impl(self, cls, block, timeout_obj);
 
 exit:
     return return_value;
@@ -248,4 +248,4 @@ _queue_SimpleQueue_qsize(simplequeueobject *self, PyObject *Py_UNUSED(ignored))
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=96cc57168d72aab1 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=acfaf0191d8935db input=a9049054013a1b77]*/
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index b71b2c4..ff1c028 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -318,8 +318,9 @@ select_select_impl(PyObject *module, PyObject *rlist, PyObject *wlist,
     if (omax > max) max = omax;
     if (emax > max) max = emax;
 
-    if (tvp)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (tvp) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     do {
         Py_BEGIN_ALLOW_THREADS
@@ -335,7 +336,7 @@ select_select_impl(PyObject *module, PyObject *rlist, PyObject *wlist,
             goto finally;
 
         if (tvp) {
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 /* bpo-35310: lists were unmodified -- clear them explicitly */
                 FD_ZERO(&ifdset);
@@ -599,7 +600,7 @@ select_poll_poll_impl(pollObject *self, PyObject *timeout_obj)
         }
 
         if (timeout >= 0) {
-            deadline = _PyTime_GetMonotonicClock() + timeout;
+            deadline = _PyDeadline_Init(timeout);
         }
     }
 
@@ -646,7 +647,7 @@ select_poll_poll_impl(pollObject *self, PyObject *timeout_obj)
         }
 
         if (timeout >= 0) {
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 poll_result = 0;
                 break;
@@ -938,8 +939,9 @@ select_devpoll_poll_impl(devpollObject *self, PyObject *timeout_obj)
     dvp.dp_nfds = self->max_n_fds;
     dvp.dp_timeout = (int)ms;
 
-    if (timeout >= 0)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (timeout >= 0) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     do {
         /* call devpoll() */
@@ -956,7 +958,7 @@ select_devpoll_poll_impl(devpollObject *self, PyObject *timeout_obj)
             return NULL;
 
         if (timeout >= 0) {
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 poll_result = 0;
                 break;
@@ -1550,7 +1552,7 @@ select_epoll_poll_impl(pyEpoll_Object *self, PyObject *timeout_obj,
         }
 
         if (timeout >= 0) {
-            deadline = _PyTime_GetMonotonicClock() + timeout;
+            deadline = _PyDeadline_Init(timeout);
         }
     }
 
@@ -1584,7 +1586,7 @@ select_epoll_poll_impl(pyEpoll_Object *self, PyObject *timeout_obj,
             goto error;
 
         if (timeout >= 0) {
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 nfds = 0;
                 break;
@@ -2172,8 +2174,9 @@ select_kqueue_control_impl(kqueue_queue_Object *self, PyObject *changelist,
         }
     }
 
-    if (ptimeoutspec)
-        deadline = _PyTime_GetMonotonicClock() + timeout;
+    if (ptimeoutspec) {
+        deadline = _PyDeadline_Init(timeout);
+    }
 
     do {
         Py_BEGIN_ALLOW_THREADS
@@ -2190,7 +2193,7 @@ select_kqueue_control_impl(kqueue_queue_Object *self, PyObject *changelist,
             goto error;
 
         if (ptimeoutspec) {
-            timeout = deadline - _PyTime_GetMonotonicClock();
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 gotevents = 0;
                 break;
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index fc58cfd..8b7ef2c 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -1221,11 +1221,7 @@ signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
                          PyObject *timeout_obj)
 /*[clinic end generated code: output=59c8971e8ae18a64 input=87fd39237cf0b7ba]*/
 {
-    struct timespec ts;
-    siginfo_t si;
-    int res;
-    _PyTime_t timeout, deadline, monotonic;
-
+    _PyTime_t timeout;
     if (_PyTime_FromSecondsObject(&timeout,
                                   timeout_obj, _PyTime_ROUND_CEILING) < 0)
         return NULL;
@@ -1235,12 +1231,16 @@ signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
         return NULL;
     }
 
-    deadline = _PyTime_GetMonotonicClock() + timeout;
+    _PyTime_t deadline = _PyDeadline_Init(timeout);
+    siginfo_t si;
 
     do {
-        if (_PyTime_AsTimespec(timeout, &ts) < 0)
+        struct timespec ts;
+        if (_PyTime_AsTimespec(timeout, &ts) < 0) {
             return NULL;
+        }
 
+        int res;
         Py_BEGIN_ALLOW_THREADS
         res = sigtimedwait(&sigset, &si, &ts);
         Py_END_ALLOW_THREADS
@@ -1259,10 +1259,10 @@ signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
         if (PyErr_CheckSignals())
             return NULL;
 
-        monotonic = _PyTime_GetMonotonicClock();
-        timeout = deadline - monotonic;
-        if (timeout < 0)
+        timeout = _PyDeadline_Get(deadline);
+        if (timeout < 0) {
             break;
+        }
     } while (1);
 
     return fill_siginfo(&si);
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index f474869..9821227 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -840,18 +840,20 @@ sock_call_ex(PySocketSockObject *s,
 
                 if (deadline_initialized) {
                     /* recompute the timeout */
-                    interval = deadline - _PyTime_GetMonotonicClock();
+                    interval = _PyDeadline_Get(deadline);
                 }
                 else {
                     deadline_initialized = 1;
-                    deadline = _PyTime_GetMonotonicClock() + timeout;
+                    deadline = _PyDeadline_Init(timeout);
                     interval = timeout;
                 }
 
-                if (interval >= 0)
+                if (interval >= 0) {
                     res = internal_select(s, writing, interval, connect);
-                else
+                }
+                else {
                     res = 1;
+                }
             }
             else {
                 res = internal_select(s, writing, timeout, connect);
@@ -4176,7 +4178,7 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
     Py_buffer pbuf;
     struct sock_send ctx;
     int has_timeout = (s->sock_timeout > 0);
-    _PyTime_t interval = s->sock_timeout;
+    _PyTime_t timeout = s->sock_timeout;
     _PyTime_t deadline = 0;
     int deadline_initialized = 0;
     PyObject *res = NULL;
@@ -4195,14 +4197,14 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
         if (has_timeout) {
             if (deadline_initialized) {
                 /* recompute the timeout */
-                interval = deadline - _PyTime_GetMonotonicClock();
+                timeout = _PyDeadline_Get(deadline);
             }
             else {
                 deadline_initialized = 1;
-                deadline = _PyTime_GetMonotonicClock() + s->sock_timeout;
+                deadline = _PyDeadline_Init(timeout);
             }
 
-            if (interval <= 0) {
+            if (timeout <= 0) {
                 PyErr_SetString(PyExc_TimeoutError, "timed out");
                 goto done;
             }
@@ -4211,7 +4213,7 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
         ctx.buf = buf;
         ctx.len = len;
         ctx.flags = flags;
-        if (sock_call_ex(s, 1, sock_send_impl, &ctx, 0, NULL, interval) < 0)
+        if (sock_call_ex(s, 1, sock_send_impl, &ctx, 0, NULL, timeout) < 0)
             goto done;
         n = ctx.result;
         assert(n >= 0);