STINNER Victor <vstin...@redhat.com> added the comment:
I dislike PR 13649 because it touch the thread module, only to fix a
faulthandler unit test. The relationship between thread stack size and
faulthandler is not obvious to me. Currently, faulthandler uses SIGSTKSZ, not
the thread stack size. faulthandler usage of the stack should be quite low: it
should need less than 1 MiB for example.
"When faulthandler.c uses sigaltstack(2), the stack size is set up with a
buffer of size SIGSTKSZ. That is, sadly, only 8k."
"A chained signal handler that needs to invoke dynamic linking will therefore
consume more than the default stack space allocated in faulthandler.c, just in
machine-state saves alone. So, the failing test is failing because its
scribbling on random memory before the allocated stack space."
Aha, that's interesting: SIGSTKSZ should be enough for 1 signal handler, but
test_register_chain calls 2 signal handlers using the same stack. Can you
please try the following patch?
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index 2331051f79..e7d13f2b2d 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -1325,7 +1325,7 @@ _PyFaulthandler_Init(int enable)
* be able to allocate memory on the stack, even on a stack overflow. If it
* fails, ignore the error. */
stack.ss_flags = 0;
- stack.ss_size = SIGSTKSZ;
+ stack.ss_size = SIGSTKSZ * 2;
stack.ss_sp = PyMem_Malloc(stack.ss_size);
if (stack.ss_sp != NULL) {
err = sigaltstack(&stack, &old_stack);
----------
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<https://bugs.python.org/issue21131>
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