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Issue #18756: os.urandom() now uses a lazily-opened persistent file descriptor, so as to avoid using many file descriptors when run in parallel from multiple threads.

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This commit is contained in:
Antoine Pitrou 2013-08-31 00:26:02 +02:00
parent 267964c837
commit 4879a963d4
4 changed files with 48 additions and 13 deletions
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55
Python/random.c
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@ -90,6 +90,7 @@ vms_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
#if !defined(MS_WINDOWS) && !defined(__VMS)
static int urandom_fd = -1;
/* Read size bytes from /dev/urandom into buffer.
Call Py_FatalError() on error. */
@ -133,18 +134,30 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
if (size <= 0)
return 0;
Py_BEGIN_ALLOW_THREADS
fd = _Py_open("/dev/urandom", O_RDONLY);
Py_END_ALLOW_THREADS
if (fd < 0)
{
if (errno == ENOENT || errno == ENXIO ||
errno == ENODEV || errno == EACCES)
PyErr_SetString(PyExc_NotImplementedError,
"/dev/urandom (or equivalent) not found");
if (urandom_fd >= 0)
fd = urandom_fd;
else {
Py_BEGIN_ALLOW_THREADS
fd = _Py_open("/dev/urandom", O_RDONLY);
Py_END_ALLOW_THREADS
if (fd < 0)
{
if (errno == ENOENT || errno == ENXIO ||
errno == ENODEV || errno == EACCES)
PyErr_SetString(PyExc_NotImplementedError,
"/dev/urandom (or equivalent) not found");
else
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
if (urandom_fd >= 0) {
/* urandom_fd was initialized by another thread while we were
not holding the GIL, keep it. */
close(fd);
fd = urandom_fd;
}
else
PyErr_SetFromErrno(PyExc_OSError);
return -1;
urandom_fd = fd;
}
Py_BEGIN_ALLOW_THREADS
@ -168,12 +181,20 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
PyErr_Format(PyExc_RuntimeError,
"Failed to read %zi bytes from /dev/urandom",
size);
close(fd);
return -1;
}
close(fd);
return 0;
}
static void
dev_urandom_close(void)
{
if (urandom_fd >= 0) {
close(urandom_fd);
urandom_fd = -1;
}
}
#endif /* !defined(MS_WINDOWS) && !defined(__VMS) */
/* Fill buffer with pseudo-random bytes generated by a linear congruent
@ -271,3 +292,11 @@ _PyRandom_Init(void)
#endif
}
}
void
_PyRandom_Fini(void)
{
#if !defined(MS_WINDOWS) && !defined(__VMS)
dev_urandom_close();
#endif
}