Issue #10798: Reject supporting concurrent.futures if the system has
too few POSIX semaphores.
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index f461b77..79c60c3 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -244,6 +244,31 @@
else:
work_item.future.set_result(result_item.result)
+_system_limits_checked = False
+_system_limited = None
+def _check_system_limits():
+ global _system_limits_checked, _system_limited
+ if _system_limits_checked:
+ if _system_limited:
+ raise NotImplementedError(_system_limited)
+ _system_limits_checked = True
+ try:
+ import os
+ nsems_max = os.sysconf("SC_SEM_NSEMS_MAX")
+ except (AttributeError, ValueError):
+ # sysconf not available or setting not available
+ return
+ if nsems_max == -1:
+ # indetermine limit, assume that limit is determined
+ # by available memory only
+ return
+ if nsems_max >= 256:
+ # minimum number of semaphores available
+ # according to POSIX
+ return
+ _system_limited = "system provides too few semaphores (%d available, 256 necessary)" % nsems_max
+ raise NotImplementedError(_system_limited)
+
class ProcessPoolExecutor(_base.Executor):
def __init__(self, max_workers=None):
"""Initializes a new ProcessPoolExecutor instance.
@@ -253,6 +278,7 @@
execute the given calls. If None or not given then as many
worker processes will be created as the machine has processors.
"""
+ _check_system_limits()
_remove_dead_thread_references()
if max_workers is None: