bpo-30768: Recompute timeout on interrupted lock (GH-4103)

Fix the pthread+semaphore implementation of
PyThread_acquire_lock_timed() when called with timeout > 0 and
intr_flag=0: recompute the timeout if sem_timedwait() is interrupted
by a signal (EINTR).

See also the PEP 475.

The pthread implementation of PyThread_acquire_lock() now fails with
a fatal error if the timeout is larger than PY_TIMEOUT_MAX, as done
in the Windows implementation.

The check prevents any risk of overflow in PyThread_acquire_lock().

Add also PY_DWORD_MAX constant.

4 files changed, 12 insertions, 14 deletions

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 72df78f..99611ee 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1363,9 +1363,11 @@ PyInit__thread(void)
     if (m == NULL)
         return NULL;
 
-    timeout_max = PY_TIMEOUT_MAX / 1000000;
-    time_max = floor(_PyTime_AsSecondsDouble(_PyTime_MAX));
+    timeout_max = (double)PY_TIMEOUT_MAX * 1e-6;
+    time_max = _PyTime_AsSecondsDouble(_PyTime_MAX);
     timeout_max = Py_MIN(timeout_max, time_max);
+    /* Round towards minus infinity */
+    timeout_max = floor(timeout_max);
 
     v = PyFloat_FromDouble(timeout_max);
     if (!v)
diff --git a/Modules/_winapi.c b/Modules/_winapi.c
index 00a26d51..7e8d4e3 100644
--- a/Modules/_winapi.c
+++ b/Modules/_winapi.c
@@ -61,8 +61,6 @@
 
 #define T_HANDLE T_POINTER
 
-#define DWORD_MAX 4294967295U
-
 /* Grab CancelIoEx dynamically from kernel32 */
 static int has_CancelIoEx = -1;
 static BOOL (CALLBACK *Py_CancelIoEx)(HANDLE, LPOVERLAPPED);
@@ -184,11 +182,11 @@ class DWORD_return_converter(CReturnConverter):
 
     def render(self, function, data):
         self.declare(data)
-        self.err_occurred_if("_return_value == DWORD_MAX", data)
+        self.err_occurred_if("_return_value == PY_DWORD_MAX", data)
         data.return_conversion.append(
             'return_value = Py_BuildValue("k", _return_value);\n')
 [python start generated code]*/
-/*[python end generated code: output=da39a3ee5e6b4b0d input=94819e72d2c6d558]*/
+/*[python end generated code: output=da39a3ee5e6b4b0d input=4527052fe06e5823]*/
 
 #include "clinic/_winapi.c.h"
 
@@ -1009,7 +1007,7 @@ _winapi_GetExitCodeProcess_impl(PyObject *module, HANDLE process)
 
     if (! result) {
         PyErr_SetFromWindowsErr(GetLastError());
-        exit_code = DWORD_MAX;
+        exit_code = PY_DWORD_MAX;
     }
 
     return exit_code;
@@ -1466,7 +1464,7 @@ _winapi_WriteFile_impl(PyObject *module, HANDLE handle, PyObject *buffer,
     }
 
     Py_BEGIN_ALLOW_THREADS
-    len = (DWORD)Py_MIN(buf->len, DWORD_MAX);
+    len = (DWORD)Py_MIN(buf->len, PY_DWORD_MAX);
     ret = WriteFile(handle, buf->buf, len, &written,
                     overlapped ? &overlapped->overlapped : NULL);
     Py_END_ALLOW_THREADS
diff --git a/Modules/clinic/_winapi.c.h b/Modules/clinic/_winapi.c.h
index 9e1fbe1..01bba36 100644
--- a/Modules/clinic/_winapi.c.h
+++ b/Modules/clinic/_winapi.c.h
@@ -460,7 +460,7 @@ _winapi_GetExitCodeProcess(PyObject *module, PyObject *arg)
         goto exit;
     }
     _return_value = _winapi_GetExitCodeProcess_impl(module, process);
-    if ((_return_value == DWORD_MAX) && PyErr_Occurred()) {
+    if ((_return_value == PY_DWORD_MAX) && PyErr_Occurred()) {
         goto exit;
     }
     return_value = Py_BuildValue("k", _return_value);
@@ -487,7 +487,7 @@ _winapi_GetLastError(PyObject *module, PyObject *Py_UNUSED(ignored))
     DWORD _return_value;
 
     _return_value = _winapi_GetLastError_impl(module);
-    if ((_return_value == DWORD_MAX) && PyErr_Occurred()) {
+    if ((_return_value == PY_DWORD_MAX) && PyErr_Occurred()) {
         goto exit;
     }
     return_value = Py_BuildValue("k", _return_value);
@@ -889,4 +889,4 @@ _winapi_WriteFile(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=afa6bd61eb0f18d2 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=fba2ad7bf1a87e4a input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index c7d8b00..661fa13 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -390,8 +390,6 @@ static int win32_can_symlink = 0;
 #endif
 #endif
 
-#define DWORD_MAX 4294967295U
-
 #ifdef MS_WINDOWS
 #define INITFUNC PyInit_nt
 #define MODNAME "nt"
@@ -3817,7 +3815,7 @@ os__getvolumepathname_impl(PyObject *module, PyObject *path)
     /* Volume path should be shorter than entire path */
     buflen = Py_MAX(buflen, MAX_PATH);
 
-    if (buflen > DWORD_MAX) {
+    if (buflen > PY_DWORD_MAX) {
         PyErr_SetString(PyExc_OverflowError, "path too long");
         return NULL;
     }