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procutil: always waiting on child processes to prevent zombies with 'hg serve'...
procutil: always waiting on child processes to prevent zombies with 'hg serve' When runbgcommand is invoked by an extension with ensurestart=False, we never called waitpid - which is fine in most cases, except if that's happening on a command server (e.g. chg), in which case the child defunct process will just sit there for as long as the server is running. The actual semantics of SIGCHLD signal handling is a lot more complex than it seems, and the POSIX standard *seems* to read that it's ignored by default and everything would just work without the waitpid if we're not listening for it, but the truth is that it's only ignored if we *explicitly* set it to SIG_IGN. We further cannot set it to SIG_IGN or to a catch-all handler across all of 'hg serve', because Python's suprocess.Popen relies on that signal, and a few specific parts of hg also set custom handlers, so instead we wait for specific PIDs in dedicated threads. I did a poor-man's benchmark of the thread creation and it seems to take about 1ms, which is way better than the 20+ms from ensurestart=True. Differential Revision: https://phab.mercurial-scm.org/D8497

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util.h
74 lines | 2.0 KiB | text/x-c | CLexer
/*
util.h - utility functions for interfacing with the various python APIs.
This software may be used and distributed according to the terms of
the GNU General Public License, incorporated herein by reference.
*/
#ifndef _HG_UTIL_H_
#define _HG_UTIL_H_
#include "compat.h"
#if PY_MAJOR_VERSION >= 3
#define IS_PY3K
#endif
/* helper to switch things like string literal depending on Python version */
#ifdef IS_PY3K
#define PY23(py2, py3) py3
#else
#define PY23(py2, py3) py2
#endif
/* clang-format off */
typedef struct {
PyObject_HEAD
char state;
int mode;
int size;
int mtime;
} dirstateTupleObject;
/* clang-format on */
extern PyTypeObject dirstateTupleType;
#define dirstate_tuple_check(op) (Py_TYPE(op) == &dirstateTupleType)
#ifndef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif
/* VC9 doesn't include bool and lacks stdbool.h based on my searching */
#if defined(_MSC_VER) || __STDC_VERSION__ < 199901L
#define true 1
#define false 0
typedef unsigned char bool;
#else
#include <stdbool.h>
#endif
static inline PyObject *_dict_new_presized(Py_ssize_t expected_size)
{
/* _PyDict_NewPresized expects a minused parameter, but it actually
creates a dictionary that's the nearest power of two bigger than the
parameter. For example, with the initial minused = 1000, the
dictionary created has size 1024. Of course in a lot of cases that
can be greater than the maximum load factor Python's dict object
expects (= 2/3), so as soon as we cross the threshold we'll resize
anyway. So create a dictionary that's at least 3/2 the size. */
return _PyDict_NewPresized(((1 + expected_size) / 2) * 3);
}
/* Convert a PyInt or PyLong to a long. Returns false if there is an
error, in which case an exception will already have been set. */
static inline bool pylong_to_long(PyObject *pylong, long *out)
{
*out = PyLong_AsLong(pylong);
/* Fast path to avoid hitting PyErr_Occurred if the value was obviously
* not an error. */
if (*out != -1) {
return true;
}
return PyErr_Occurred() == NULL;
}
#endif /* _HG_UTIL_H_ */