Clean Up nogil Warning From Parsers (#30369)

Author: WillAyd

pandas/_libs/parsers.pyx

@@ -171,12 +171,9 @@ cdef extern from "parser/tokenizer.h":
         int64_t skip_first_N_rows
         int64_t skipfooter
         # pick one, depending on whether the converter requires GIL
-        float64_t (*double_converter_nogil)(const char *, char **,
-                                            char, char, char,
-                                            int, int *, int *) nogil
-        float64_t (*double_converter_withgil)(const char *, char **,
-                                              char, char, char,
-                                              int, int *, int *)
+        float64_t (*double_converter)(const char *, char **,
+                                      char, char, char,
+                                      int, int *, int *) nogil
 
         #  error handling
         char *warn_msg
@@ -469,16 +466,11 @@ cdef class TextReader:
 
         if float_precision == "round_trip":
             # see gh-15140
-            #
-            # Our current roundtrip implementation requires the GIL.
-            self.parser.double_converter_nogil = NULL
-            self.parser.double_converter_withgil = round_trip
+            self.parser.double_converter = round_trip
         elif float_precision == "high":
-            self.parser.double_converter_withgil = NULL
-            self.parser.double_converter_nogil = precise_xstrtod
+            self.parser.double_converter = precise_xstrtod
         else:
-            self.parser.double_converter_withgil = NULL
-            self.parser.double_converter_nogil = xstrtod
+            self.parser.double_converter = xstrtod
 
         if isinstance(dtype, dict):
             dtype = {k: pandas_dtype(dtype[k])
@@ -1663,22 +1655,12 @@ cdef _try_double(parser_t *parser, int64_t col,
     result = np.empty(lines, dtype=np.float64)
     data = <float64_t *>result.data
     na_fset = kset_float64_from_list(na_flist)
-    if parser.double_converter_nogil != NULL:  # if it can run without the GIL
-        with nogil:
-            error = _try_double_nogil(parser, parser.double_converter_nogil,
-                                      col, line_start, line_end,
-                                      na_filter, na_hashset, use_na_flist,
-                                      na_fset, NA, data, &na_count)
-    else:
-        assert parser.double_converter_withgil != NULL
-        error = _try_double_nogil(parser,
-                                  <float64_t (*)(const char *, char **,
-                                                 char, char, char,
-                                                 int, int *, int *)
-                                  nogil>parser.double_converter_withgil,
+    with nogil:
+        error = _try_double_nogil(parser, parser.double_converter,
                                   col, line_start, line_end,
                                   na_filter, na_hashset, use_na_flist,
                                   na_fset, NA, data, &na_count)
+
     kh_destroy_float64(na_fset)
     if error != 0:
         return None, None

pandas/_libs/src/parser/tokenizer.c

@@ -1774,11 +1774,18 @@ double precise_xstrtod(const char *str, char **endptr, char decimal,
 
 double round_trip(const char *p, char **q, char decimal, char sci, char tsep,
                   int skip_trailing, int *error, int *maybe_int) {
+    // This is called from a nogil block in parsers.pyx
+    // so need to explicitly get GIL before Python calls
+    PyGILState_STATE gstate;
+    gstate = PyGILState_Ensure();
+
     double r = PyOS_string_to_double(p, q, 0);
     if (maybe_int != NULL) *maybe_int = 0;
     if (PyErr_Occurred() != NULL) *error = -1;
     else if (r == Py_HUGE_VAL) *error = (int)Py_HUGE_VAL;
     PyErr_Clear();
+
+    PyGILState_Release(gstate);
     return r;
 }
 

pandas/_libs/src/parser/tokenizer.h

@@ -155,11 +155,8 @@ typedef struct parser_t {
     PyObject *skipfunc;
     int64_t skip_first_N_rows;
     int64_t skip_footer;
-    // pick one, depending on whether the converter requires GIL
-    double (*double_converter_nogil)(const char *, char **,
-                                     char, char, char, int, int *, int *);
-    double (*double_converter_withgil)(const char *, char **,
-                                       char, char, char, int, int *, int *);
+    double (*double_converter)(const char *, char **,
+                               char, char, char, int, int *, int *);
 
     // error handling
     char *warn_msg;
@@ -226,6 +223,8 @@ double xstrtod(const char *p, char **q, char decimal, char sci, char tsep,
 double precise_xstrtod(const char *p, char **q, char decimal,
                        char sci, char tsep, int skip_trailing,
                        int *error, int *maybe_int);
+
+// GH-15140 - round_trip requires and acquires the GIL on its own
 double round_trip(const char *p, char **q, char decimal, char sci, char tsep,
                   int skip_trailing, int *error, int *maybe_int);
 int to_boolean(const char *item, uint8_t *val);