mirror of https://github.com/python/cpython
Merged revisions 68460 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r68460 | kristjan.jonsson | 2009-01-09 14:31:26 -0600 (Fri, 09 Jan 2009) | 1 line Issue 4293: Make Py_AddPendingCall() thread safe ........
This commit is contained in:
Benjamin Peterson
parent
92d0a6a559
commit
e5bf383959
168
Python/ceval.c
168
Python/ceval.c
|
|
@ -205,6 +205,7 @@ PyEval_GetCallStats(PyObject *self)
|
|||
#include "pythread.h"
|
||||
|
||||
static PyThread_type_lock interpreter_lock = 0; /* This is the GIL */
|
||||
static PyThread_type_lock pending_lock = 0; /* for pending calls */
|
||||
static long main_thread = 0;
|
||||
|
||||
int
|
||||
|
|
@ -276,6 +277,7 @@ PyEval_ReInitThreads(void)
|
|||
adding a new function to each thread_*.h. Instead, just
|
||||
create a new lock and waste a little bit of memory */
|
||||
interpreter_lock = PyThread_allocate_lock();
|
||||
pending_lock = PyThread_allocate_lock();
|
||||
PyThread_acquire_lock(interpreter_lock, 1);
|
||||
main_thread = PyThread_get_thread_ident();
|
||||
|
||||
|
|
@ -348,19 +350,145 @@ PyEval_RestoreThread(PyThreadState *tstate)
|
|||
#ifdef WITH_THREAD
|
||||
Any thread can schedule pending calls, but only the main thread
|
||||
will execute them.
|
||||
There is no facility to schedule calls to a particular thread, but
|
||||
that should be easy to change, should that ever be required. In
|
||||
that case, the static variables here should go into the python
|
||||
threadstate.
|
||||
#endif
|
||||
*/
|
||||
|
||||
XXX WARNING! ASYNCHRONOUSLY EXECUTING CODE!
|
||||
#ifdef WITH_THREAD
|
||||
|
||||
/* The WITH_THREAD implementation is thread-safe. It allows
|
||||
scheduling to be made from any thread, and even from an executing
|
||||
callback.
|
||||
*/
|
||||
|
||||
#define NPENDINGCALLS 32
|
||||
static struct {
|
||||
int (*func)(void *);
|
||||
void *arg;
|
||||
} pendingcalls[NPENDINGCALLS];
|
||||
static int pendingfirst = 0;
|
||||
static int pendinglast = 0;
|
||||
static volatile int pendingcalls_to_do = 1; /* trigger initialization of lock */
|
||||
static char pendingbusy = 0;
|
||||
|
||||
int
|
||||
Py_AddPendingCall(int (*func)(void *), void *arg)
|
||||
{
|
||||
int i, j, result=0;
|
||||
PyThread_type_lock lock = pending_lock;
|
||||
|
||||
/* try a few times for the lock. Since this mechanism is used
|
||||
* for signal handling (on the main thread), there is a (slim)
|
||||
* chance that a signal is delivered on the same thread while we
|
||||
* hold the lock during the Py_MakePendingCalls() function.
|
||||
* This avoids a deadlock in that case.
|
||||
* Note that signals can be delivered on any thread. In particular,
|
||||
* on Windows, a SIGINT is delivered on a system-created worker
|
||||
* thread.
|
||||
* We also check for lock being NULL, in the unlikely case that
|
||||
* this function is called before any bytecode evaluation takes place.
|
||||
*/
|
||||
if (lock != NULL) {
|
||||
for (i = 0; i<100; i++) {
|
||||
if (PyThread_acquire_lock(lock, NOWAIT_LOCK))
|
||||
break;
|
||||
}
|
||||
if (i == 100)
|
||||
return -1;
|
||||
}
|
||||
|
||||
i = pendinglast;
|
||||
j = (i + 1) % NPENDINGCALLS;
|
||||
if (j == pendingfirst) {
|
||||
result = -1; /* Queue full */
|
||||
} else {
|
||||
pendingcalls[i].func = func;
|
||||
pendingcalls[i].arg = arg;
|
||||
pendinglast = j;
|
||||
}
|
||||
/* signal main loop */
|
||||
_Py_Ticker = 0;
|
||||
pendingcalls_to_do = 1;
|
||||
if (lock != NULL)
|
||||
PyThread_release_lock(lock);
|
||||
return result;
|
||||
}
|
||||
|
||||
int
|
||||
Py_MakePendingCalls(void)
|
||||
{
|
||||
int i;
|
||||
int r = 0;
|
||||
|
||||
if (!pending_lock) {
|
||||
/* initial allocation of the lock */
|
||||
pending_lock = PyThread_allocate_lock();
|
||||
if (pending_lock == NULL)
|
||||
return -1;
|
||||
}
|
||||
|
||||
/* only service pending calls on main thread */
|
||||
if (main_thread && PyThread_get_thread_ident() != main_thread)
|
||||
return 0;
|
||||
/* don't perform recursive pending calls */
|
||||
if (pendingbusy)
|
||||
return 0;
|
||||
pendingbusy = 1;
|
||||
/* perform a bounded number of calls, in case of recursion */
|
||||
for (i=0; i<NPENDINGCALLS; i++) {
|
||||
int j;
|
||||
int (*func)(void *);
|
||||
void *arg;
|
||||
|
||||
/* pop one item off the queue while holding the lock */
|
||||
PyThread_acquire_lock(pending_lock, WAIT_LOCK);
|
||||
j = pendingfirst;
|
||||
if (j == pendinglast) {
|
||||
func = NULL; /* Queue empty */
|
||||
} else {
|
||||
func = pendingcalls[j].func;
|
||||
arg = pendingcalls[j].arg;
|
||||
pendingfirst = (j + 1) % NPENDINGCALLS;
|
||||
}
|
||||
pendingcalls_to_do = pendingfirst != pendinglast;
|
||||
PyThread_release_lock(pending_lock);
|
||||
/* having released the lock, perform the callback */
|
||||
if (func == NULL)
|
||||
break;
|
||||
r = func(arg);
|
||||
if (r)
|
||||
break;
|
||||
}
|
||||
pendingbusy = 0;
|
||||
return r;
|
||||
}
|
||||
|
||||
#else /* if ! defined WITH_THREAD */
|
||||
|
||||
/*
|
||||
WARNING! ASYNCHRONOUSLY EXECUTING CODE!
|
||||
This code is used for signal handling in python that isn't built
|
||||
with WITH_THREAD.
|
||||
Don't use this implementation when Py_AddPendingCalls() can happen
|
||||
on a different thread!
|
||||
|
||||
There are two possible race conditions:
|
||||
(1) nested asynchronous registry calls;
|
||||
(2) registry calls made while pending calls are being processed.
|
||||
While (1) is very unlikely, (2) is a real possibility.
|
||||
(1) nested asynchronous calls to Py_AddPendingCall()
|
||||
(2) AddPendingCall() calls made while pending calls are being processed.
|
||||
|
||||
(1) is very unlikely because typically signal delivery
|
||||
is blocked during signal handling. So it should be impossible.
|
||||
(2) is a real possibility.
|
||||
The current code is safe against (2), but not against (1).
|
||||
The safety against (2) is derived from the fact that only one
|
||||
thread (the main thread) ever takes things out of the queue.
|
||||
|
||||
XXX Darn! With the advent of thread state, we should have an array
|
||||
of pending calls per thread in the thread state! Later...
|
||||
thread is present, interrupted by signals, and that the critical
|
||||
section is protected with the "busy" variable. On Windows, which
|
||||
delivers SIGINT on a system thread, this does not hold and therefore
|
||||
Windows really shouldn't use this version.
|
||||
The two threads could theoretically wiggle around the "busy" variable.
|
||||
*/
|
||||
|
||||
#define NPENDINGCALLS 32
|
||||
|
|
@ -370,7 +498,7 @@ static struct {
|
|||
} pendingcalls[NPENDINGCALLS];
|
||||
static volatile int pendingfirst = 0;
|
||||
static volatile int pendinglast = 0;
|
||||
static volatile int things_to_do = 0;
|
||||
static volatile int pendingcalls_to_do = 0;
|
||||
|
||||
int
|
||||
Py_AddPendingCall(int (*func)(void *), void *arg)
|
||||
|
|
@ -378,8 +506,6 @@ Py_AddPendingCall(int (*func)(void *), void *arg)
|
|||
static volatile int busy = 0;
|
||||
int i, j;
|
||||
/* XXX Begin critical section */
|
||||
/* XXX If you want this to be safe against nested
|
||||
XXX asynchronous calls, you'll have to work harder! */
|
||||
if (busy)
|
||||
return -1;
|
||||
busy = 1;
|
||||
|
|
@ -394,7 +520,7 @@ Py_AddPendingCall(int (*func)(void *), void *arg)
|
|||
pendinglast = j;
|
||||
|
||||
_Py_Ticker = 0;
|
||||
things_to_do = 1; /* Signal main loop */
|
||||
pendingcalls_to_do = 1; /* Signal main loop */
|
||||
busy = 0;
|
||||
/* XXX End critical section */
|
||||
return 0;
|
||||
|
|
@ -404,14 +530,10 @@ int
|
|||
Py_MakePendingCalls(void)
|
||||
{
|
||||
static int busy = 0;
|
||||
#ifdef WITH_THREAD
|
||||
if (main_thread && PyThread_get_thread_ident() != main_thread)
|
||||
return 0;
|
||||
#endif
|
||||
if (busy)
|
||||
return 0;
|
||||
busy = 1;
|
||||
things_to_do = 0;
|
||||
pendingcalls_to_do = 0;
|
||||
for (;;) {
|
||||
int i;
|
||||
int (*func)(void *);
|
||||
|
|
@ -424,7 +546,7 @@ Py_MakePendingCalls(void)
|
|||
pendingfirst = (i + 1) % NPENDINGCALLS;
|
||||
if (func(arg) < 0) {
|
||||
busy = 0;
|
||||
things_to_do = 1; /* We're not done yet */
|
||||
pendingcalls_to_do = 1; /* We're not done yet */
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
|
|
@ -432,6 +554,8 @@ Py_MakePendingCalls(void)
|
|||
return 0;
|
||||
}
|
||||
|
||||
#endif /* WITH_THREAD */
|
||||
|
||||
|
||||
/* The interpreter's recursion limit */
|
||||
|
||||
|
|
@ -518,7 +642,7 @@ static int _Py_TracingPossible = 0;
|
|||
/* for manipulating the thread switch and periodic "stuff" - used to be
|
||||
per thread, now just a pair o' globals */
|
||||
int _Py_CheckInterval = 100;
|
||||
volatile int _Py_Ticker = 100;
|
||||
volatile int _Py_Ticker = 0; /* so that we hit a "tick" first thing */
|
||||
|
||||
PyObject *
|
||||
PyEval_EvalCode(PyCodeObject *co, PyObject *globals, PyObject *locals)
|
||||
|
|
@ -903,7 +1027,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
|
|||
/* Do periodic things. Doing this every time through
|
||||
the loop would add too much overhead, so we do it
|
||||
only every Nth instruction. We also do it if
|
||||
``things_to_do'' is set, i.e. when an asynchronous
|
||||
``pendingcalls_to_do'' is set, i.e. when an asynchronous
|
||||
event needs attention (e.g. a signal handler or
|
||||
async I/O handler); see Py_AddPendingCall() and
|
||||
Py_MakePendingCalls() above. */
|
||||
|
|
@ -919,12 +1043,12 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
|
|||
#ifdef WITH_TSC
|
||||
ticked = 1;
|
||||
#endif
|
||||
if (things_to_do) {
|
||||
if (pendingcalls_to_do) {
|
||||
if (Py_MakePendingCalls() < 0) {
|
||||
why = WHY_EXCEPTION;
|
||||
goto on_error;
|
||||
}
|
||||
if (things_to_do)
|
||||
if (pendingcalls_to_do)
|
||||
/* MakePendingCalls() didn't succeed.
|
||||
Force early re-execution of this
|
||||
"periodic" code, possibly after
|
||||
|
|
|
|||
Loading…
Reference in New Issue