test_signal: test_stress_modifying_handlers() failed on s390x SLES 3.x

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See also:

• test_stress_delivery_dependent() of test_signal randomly fails on AMD64 Debian root 3.6/3.x #75032
• test_signal: test_stress_modifying_handlers() crash with SIGSEGV on GHA macOS (macOS-12.7) #110083

s390x SLES 3.x:

== CPU count: 4
...
0:03:27 load avg: 5.22 [280/467/1] test_signal failed (1 failure) (1 min 10 sec) -- running (1): test.test_multiprocessing_spawn.test_processes (38.4 sec)
(...)
FAIL: test_stress_modifying_handlers (test.test_signal.StressTest.test_stress_modifying_handlers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Lib/test/test_signal.py", line 1374, in test_stress_modifying_handlers
    self.assertGreater(num_received_signals, 0)
AssertionError: 0 not greater than 0

Test pass when re-run in verbose mode.

build: https://buildbot.python.org/all/#/builders/540/builds/6801

Linked PRs

• gh-110647: Fix signal test_stress_modifying_handlers() #110650
• [3.12] gh-110647: Fix signal test_stress_modifying_handlers() (GH-110650) #110658
• [3.11] gh-110647: Fix signal test_stress_modifying_handlers() (GH-110650) #110659

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Change to make the error more likely:

diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index 2a1a1ee22f..d7017c3281 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -1339,8 +1339,8 @@ def set_interrupts():
                 num_sent_signals += 1
 
         def cycle_handlers():
-            while num_sent_signals < 100:
-                for i in range(20000):
+            while num_sent_signals < 10:
+                for i in range(2000):
                     # Cycle between a Python-defined and a non-Python handler
                     for handler in [custom_handler, signal.SIG_IGN]:
                         signal.signal(signum, handler)