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bpo-41710: PyThread_acquire_lock_timed() clamps the timout #28643

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Merged
vstinner merged 5 commits into from
Sep 30, 2021
Merged

bpo-41710: PyThread_acquire_lock_timed() clamps the timout #28643

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8f791d9
bpo-41710: PyThread_acquire_lock_timed() clamps the timout
vstinner Sep 29, 2021
d8e1989
Fix test
vstinner Sep 30, 2021
1cd1474
Fix PY_TIMEOUT_MAX on Windows
vstinner Sep 30, 2021
01f5238
Fix typo
vstinner Sep 30, 2021
60bc581
Fix signed/unsigned comparison
vstinner Sep 30, 2021
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bpo-41710: PyThread_acquire_lock_timed() clamps the timout 
PyThread_acquire_lock_timed() now clamps the timeout into the
[_PyTime_MIN; _PyTime_MAX] range (_PyTime_t type) if it is too large,
rather than calling Py_FatalError() which aborts the process.

PyThread_acquire_lock_timed() no longer uses
MICROSECONDS_TO_TIMESPEC() to compute sem_timedwait() argument, but
_PyTime_GetSystemClock() and _PyTime_AsTimespec_truncate().
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@vstinner
vstinner committed Sep 30, 2021
commit 8f791d9081bfb1c9abf104f01a9c49ec1039f908
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/C API/2021-09-30-03-14-35.bpo-41710.DDWJKx.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
The PyThread_acquire_lock_timed() function now clamps the timeout if it is
too large, rather than aborting the process. Patch by Victor Stinner.
8 changes: 7 additions & 1 deletion Python/thread_nt.h
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Expand Up @@ -312,7 +312,13 @@ PyThread_acquire_lock_timed(PyThread_type_lock aLock,
if (microseconds % 1000 > 0)
++milliseconds;
if (milliseconds > PY_DWORD_MAX) {
Py_FatalError("Timeout larger than PY_TIMEOUT_MAX");
// bpo-41710: PyThread_acquire_lock_timed() cannot report timeout
// overflow to the caller, so clamp the timeout to
// [0, PY_DWORD_MAX] milliseconds.
//
// _thread.Lock.acquire() and _thread.RLock.acquire() raise an
// OverflowError if microseconds is greater than PY_TIMEOUT_MAX.
milliseconds = PY_DWORD_MAX;
}
}
else {
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61 changes: 32 additions & 29 deletions Python/thread_pthread.h
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Expand Up @@ -433,33 +433,45 @@ PyThread_acquire_lock_timed(PyThread_type_lock lock, PY_TIMEOUT_T microseconds,
PyLockStatus success;
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
struct timespec ts;
_PyTime_t deadline = 0;

(void) error; /* silence unused-but-set-variable warning */
dprintf(("PyThread_acquire_lock_timed(%p, %lld, %d) called\n",
lock, microseconds, intr_flag));

if (microseconds > PY_TIMEOUT_MAX) {
Py_FatalError("Timeout larger than PY_TIMEOUT_MAX");
_PyTime_t timeout;
if (microseconds >= 0) {
_PyTime_t ns;
if (microseconds < _PyTime_MAX / 1000) {
ns = microseconds * 1000;
}
else {
// bpo-41710: PyThread_acquire_lock_timed() cannot report timeout
// overflow to the caller, so clamp the timeout to
// [_PyTime_MIN, _PyTime_MAX].
//
// _thread.Lock.acquire() and _thread.RLock.acquire() raise an
// OverflowError if microseconds is greater than PY_TIMEOUT_MAX.
ns = _PyTime_MAX;
}
timeout = _PyTime_FromNanoseconds(ns);
}
else {
timeout = _PyTime_FromNanoseconds(-1);
}

if (microseconds > 0) {
MICROSECONDS_TO_TIMESPEC(microseconds, ts);

if (!intr_flag) {
/* cannot overflow thanks to (microseconds > PY_TIMEOUT_MAX)
check done above */
_PyTime_t timeout = _PyTime_FromNanoseconds(microseconds * 1000);
deadline = _PyTime_GetMonotonicClock() + timeout;
}
_PyTime_t deadline = 0;
if (timeout > 0 && !intr_flag) {
deadline = _PyTime_GetMonotonicClock() + timeout;
}

while (1) {
if (microseconds > 0) {
if (timeout > 0) {
_PyTime_t t = _PyTime_GetSystemClock() + timeout;
struct timespec ts;
_PyTime_AsTimespec_clamp(t, &ts);
status = fix_status(sem_timedwait(thelock, &ts));
}
else if (microseconds == 0) {
else if (timeout == 0) {
status = fix_status(sem_trywait(thelock));
}
else {
Expand All @@ -472,32 +484,23 @@ PyThread_acquire_lock_timed(PyThread_type_lock lock, PY_TIMEOUT_T microseconds,
break;
}

if (microseconds > 0) {
if (timeout > 0) {
/* wait interrupted by a signal (EINTR): recompute the timeout */
_PyTime_t dt = deadline - _PyTime_GetMonotonicClock();
if (dt < 0) {
_PyTime_t timeout = deadline - _PyTime_GetMonotonicClock();
if (timeout < 0) {
status = ETIMEDOUT;
break;
}
else if (dt > 0) {
_PyTime_t realtime_deadline = _PyTime_GetSystemClock() + dt;
_PyTime_AsTimespec_clamp(realtime_deadline, &ts);
/* no need to update microseconds value, the code only care
if (microseconds > 0 or (microseconds == 0). */
}
else {
microseconds = 0;
}
}
}

/* Don't check the status if we're stopping because of an interrupt. */
if (!(intr_flag && status == EINTR)) {
if (microseconds > 0) {
if (timeout > 0) {
if (status != ETIMEDOUT)
CHECK_STATUS("sem_timedwait");
}
else if (microseconds == 0) {
else if (timeout == 0) {
if (status != EAGAIN)
CHECK_STATUS("sem_trywait");
}
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